You're not getting "divorced", you're getting divorced. Pretending you're not really married and not getting a real divorce isn't doing you any favors.

You don't necessarily need a lawyer for a divorce (we didn't, outside quick advice) but based on what you're posting here... I would consult a lawyer. Concepts of marital property vs separate property, and whether or not you're in a community property state really matter, and it doesn't seem like you've integrated those key concepts into your plan. Like if you live in a community property state, half the house, and car, etc is his. If not, then anything he helped with becomes co-mingled, and there's a claim there. If he mowed the lawn, or paid a water bill, that's all it takes sometimes - he has an interest in the house as entitled to at least a share of its sale.