I would show him some of the milder stuff, think choking, etc. Try to lead by example with dirty talking. It's super awkward until you get the hang of it, but there's tons of porn online that he can use as an example (video and written). Communicate through anything you try, and try to guide him to do whatever you want him to do. Ask if he's comfortable. After sex, tell him how much you liked when he did ___. Best of luck!

Brutal honesty time - you have already cheated on your partner emotionally. I also reallllly dislike when people say they're "worried" they might cheat on their partner as though they have no control over the situation. I'm sure you've heard plenty of horror stories about dating a coworker, but consider if your coworker is only interesting to you because you're hitting a slump in a long relationship. If you don't want to be with your partner (which you clearly do not), just end the relationship. Would you rather lead someone on or live life as you want to live it? I know that living together complicates things; see if there's a couple friends who have a couch for you to crash on while you look for a new place and just break up with your partner.

I don't have experience with this, but it will take a lot of time to move on from this. It's something that you've dreamed about for a really long time, and it's OK if that is a deciding factor in your relationship. It's also totally OK if not wanting to get married is a deciding factor in his. It sounds like you have made your choice, but I would suggest taking some time alone to really really think about this. Are those memories you are truly okay missing out on, or are they memories you're telling yourself are ok to miss out on because it hurts to think wanting marriage could lose you your bf?

It's an incredibly hard thing when nobody is in the wrong and you realize that you're just different. Don't make a decision you don't want for the sake of somebody else. If you're positive about not getting married, try to shift the mindset. Instead of "I wish I could have gone shopping for my wedding dress," think "I have a couple hundred/thousand dollars to spend on something else" Instead of "I don't get to share my love for my partner with others," think "I cherish what my partner and I have wherever we are".

Like I said, it's okay to take some time adjusting to this new change in your life. Just be sure that it is the right decision.