You don't sound like a meanie at all. What you are doing about the accounts is the responsible thing to do, as well as changing the one account and putting your son's name on it. After all, you don't know what your h will or will not do. You've been living the life of a single person for quite some time and it's been time to change things over to your name.
As for your h, who knows why he wants to spend time w/you. It could be any number of reasons, but I wouldn't think twice about it. If the contact doesn't bother you then, continue...but if you find that his presence is starting to annoy you, then limit the contact.
BTW, he's not moved one inch for quite some time. He's quite comfortable where he's at and most likely won't budge unless something changes in his life.
I also agree that it's very wise to have your son's party outside the home. Less headaches all the way around.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
