You are right that this is going to be messy, and the longer you delay it the worse it will probably be for you because you are setting a bad status quo right now. The problem is deep down you still care about her, and deep down she wants you to drop dead, so she is going to keep steamrolling you. My advice is to consult with a couple of lawyers to find a fair, reasonable judgement in your area, propose something close to this but a little bit better for you, do this through mediation if that is normally done in your area, and don't give up anything in mediation past the fair "midpoint" (try to think of things to offer in negotiation that have value to her, but not to you. Like right of first refusal, expediency, more upfront cash vs long term support etc), and when that breaks down you get a lawyer to fight this out for you.
A fair proposal may be to start 50-50 immediately (delayed 50-50 = never 50-50!), max 2 years of spousal support (same amount of time she has been unemployed), she vacates the house in 3 months (it will never sell if she is in it, and this gives you a few months to get it ready for spring sales season), specify 50-50 for activity and college expenses (you will thank yourself in 15 years), and impute her income at the max of what she could make full time (Its no longer your job to support her dreams of part time work or a lower earning career path - she can figure that out on her own). Offer her right of first refusal in negotiation as a carrot because she can get this anyways. This means she has every right to watch them instead of daycare on your days if she wants to - but I suspect reality will set in and she will be too busy working so long as you don't fold on the financials. And stop thinking that them being with your WAW is better than daycare, and using this as an excuse not to fight on custody. First of all, this is just not a tenable option given that it requires you to burn through your savings. And, I promise that you will quickly change your mind when she starts attempting to alienate them from you and new guys are spending more time with them than you, and by then it will probably be impossible to change status quo to get more custody.
After you send your fair proposal in writing or mediation she will immediately reject this offer and counter with a proposal for you to go die in a hole but keep giving her lots of money. At that point you need to retain your lawyer and hide behind them. Your job is to push or contain (if they start overspending) your lawyer from behind, your lawyer's job is to negotiate with your WAW or her lawyer. Whenever she attacks you, simply refuse to discuss legal matters with her.
