You just do it. I know, not helpful, so I will break it down.

First, assess what you share that you need to deal with. If you have stuff of his to return, if he has stuff of yours you want back, if he has access to your money or keys to your place. For the latter items- change the passwords/get rid of accounts he has access too, and try and get the keys back a day or two before you break up with an excuse (friend is stopping by so I need to give them the spare). Also take this time to collect your shit- quietly- from his place.

Second, break up. Go to his place, with his stuff, and break it off. Keep it short and simple "this isn't working for me, as we discussed X, Y, Z, and I am ending the relationship." Now, this is where it gets hard, because he is going to argue with you, and you simply do not participate. I learned this from a boss about firing people; you have made the decision, you don't need to justify it, you don't need to prove them wrong. Let him say what he needs to say- within reason- and you simply nod and show empathy, and end with- well I disagree and have made my decision. Sidenote: If you worry he will be angry/violent, break up in a public place instead where you have your own transportation. A walk in the park or a beer garden is good for this, not a restaurant where you have to wait for the check! Coffee shops are okay but sometimes can be very quiet. Basically, a public place where you can actually have the conversation without feeling like you have an audience, and where you can escape.

Third, do not respond to attempts at communication. You don't have to start out by blocking him, but you need to commit to "I need full space apart for awhile before even figuring out if we can be friends." If he texts you about very practical things- do you have my hoodie- you can respond and keep it brief, no small talk, solve the problem, end convo. If he starts harassing you or you think you are caving, then you silence the convo or block him. I find blocking hard because I worry it was harsh (I liked this person at one point, they weren't abusive, it just didn't work out), so just control your responses, don't get dragged in to conversation, and ask him to stop or you will block him if he is like bombing you with "i miss you."

Fourth, sorry you are a woman. Because of that, I have to tell you the following: Besides breaking up in a public/safe place, you also need to be careful for the few weeks after breaking up. Maybe stay with a friend/family if you live alone or have someone stay with you. Vary your schedule a little if you can (aka, you always leave for work at 8am, maybe go in early and get coffee for a few day). Always be very vigilant of coming home and leaving home, same with work, school, or other places you frequent. Some of this is good breakup advice regardless of safety- go visit friends in a city over, have a slumber party and eat sugar, stay with family- and yes, is this all a little nuts? Sure, but it is better to spend two weeks being a bit paranoid and then laughing it off than it is to be...on Forensic Files.

So I think there are two equally good ways to split finances.

1. Based on income: The person who makes more pays for more (rent, utilities) based on a percentage of their income, and then you decide on how you split other expense like vacations and dates. It isn't practical to split a dinner bill 60/40 or whatever, so you figure out a system of expectations for dates, and then of course each vacation can be discussed as it comes up. I think based on income is the better option when two people are married or really solid in their relationship, because then it truly is a joint partnership.
2. 50/50 but the budget is based on the lower earner: You split your expenses equally, but where you live and the other living expenses are based on you, as the lower earner. For example, if I can afford $1000 in rent and my partner can only afford $500, we find a place that fits his lower budget. That way it isn't just an equal split, but fair to the lower earner. I think this is better for couples who aren't ready for "life together" but just starting out living together, or where there is a big disparity on the value of money (one is a saver, one is a spender).

And then either way, you shouldn't be going in to debt for dates, gifts, and vacations. When a weekend trip comes up, it is fine to say "I can't afford that." I pay for most of the vacations with my partner, because he is on a limited income. I want to go on vacation, and I want him there with me, so I have no problem paying. It is totally fine to tell your partner when you can't afford something- a fancy restaurant, a weekend trip- and then they can decide if they want to pay or to pick a more economical activity. If you just say "i can't afford that" then you aren't expecting them to pay, which of course you shouldn't, you are just being honest about your finances.

So being child free is not the same as not ever being around children.

I am child free and would probably have a child free wedding, but that's because there are not a lot of little ones running around my family. I have a niece who is 12 that I would absolutely NEED at my wedding and she acts like an adult so with her included I still see it as a child free wedding. But if my partner and I had more young kids in the family, I can see us having kids at the wedding, but I'd be child free in regards to my guests bringing kids I didn't really know.

Sebby and Addie have decided to have children at their wedding. This has nothing to do with you. If you are so terrified of children you can't share space with them, then don't go. But to make this out as an affront to you and your lifestyle is so remarkably selfish and ridiculous that of course your girlfriend is wondering what future there is with you.

These people having children at their wedding is their decision, and as I mention in my first paragraph, a lot of people rethink what they want as they age, their circles change, etc. Or, maybe Sebby did cave to pressure from family, and if so, who cares? How does you not going change that at all?

Sit there all alone on your moral, child free mountain top, and watch life pass you by.

Send her a text message- as evidence- telling her you will not be going to stay elsewhere, that is your home, you are on the lease, and if she is uncomfortable with you there, she can go stay somewhere else. If you can, bring a friend home with you to make sure you have a witness, or at least have your phone recording when you get home.

You do not need to leave your home right away, and if she doesn't want to be around you, she can leave. You should also tell her if she doesn't want to live with you anymore, you both need to figure out how to break the lease and you will not be covering the full bills anymore. My guess is that threat alone will have her walking back her empty threats.

And if you get access to the home- the police can help you get that access since you are on the lease- then gather your most valuable items and keep them somewhere safe.

Record EVERYTHING once you are home, until she either leaves or you have a calm conversation.