I would base it on your base income so you aren’t in a world of hurt if for some reason the bonus doesn’t go thru or severely reduces in the future. Unless you build up enough of a cash emergency fund that it’s not an issue.

With that type of income your overall savings seems to be light though. I would start saving a higher percentage of your overall income…like maybe the entire bonus.

Never take money from your 401k. You didn’t even mention that you’ll have to pay a penalty/taxes to withdraw from your 401k so you’ll be taking out far more than you’ll be using.

Also, stop thinking of rent as throwing away money. It’s money that buys you housing. You can be much more flexible renting too. Move to a different neighborhood. Move to a smaller place to save money. Buying a house can be a hindrance in many circumstances and can come with many additional expenses. Just go to a home improvement store on the weekend and watch all the happy homeowners throwing away money on plants, mulch, ceiling fans, French doors, new knobs for the cabinets.

Electrician, pipe fitter, welder… plenty of trades pay decent wages.

Stay away from these situations. They only cause problems to intermingle your finances with your in-laws. Let them do what they want and they can put in their will what they want to happen with their property when they die. Don’t get mixed up with it now.