normally i would say just throw all the funds in one account and call it good. once that spending issue is cleared up and everyone is on the same page, then it can just be a simple all in throw the money in one account and be done but until then i think transparency but discretion.

unless he has a lot in his separate savings account the fact that he thinks spending the whole joint account without warning is a bit concerning financially.

since you have a house & other short term goals I would just put the bonus in a HYSA. you have enough in savings for the short term so if you say the house is a 7-10+ year goal to purchase then there is nothing wrong with a brokerage account to roll the dice that you can turn the bonus money into a bit more