Pretty sure we are circling the drain to divorce and I need advice

I just wrote a huge long post and accidentally deleted it. 😭 so I apologize if this one is lacking key details.

TLDR: married a long time, crappy marriage, took out a large home improvement loan right as the marriage is imploding. How to handle that situation and also how to break it to my son, if the inevitable is actually happening now.

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My husband (50) and I (51) have been married almost 17 years and have a 16-yr old son. My husband has made most of our years together so very difficult. He was an alcoholic until 2020 when he almost died of - what we found out was - cirrhosis. He still has it of course but no longer drinks. He didn’t work almost our whole marriage (the alcoholism plus the extreme anxiety that he was chasing), so my income alone sustained us for well over a decade. He works now and makes good money but I still make more. He’s emotionally and mentally abusive. He says that his attitude is directly attributable to a lack of sex. But he treats me like a personal assistant that he can’t stand (to say the least), so how does that make me want to have sex?

I should’ve gotten out a long time ago, but I’ve been trying to bide my time until my son is 18 to avoid custody and child support issues. But things have been so bad recently that I don’t really think that’s going to pan out.

Here’s the rub. We literally just took out a huge home improvement loan (personal loan so not tied to the house) to replace the siding and roof on our mid-80s house. The wood siding is original and is literally starting to rot and fall off, which is turning it in an eyesore. So I desperately want it done. But - because my husband and I have been doing particularly bad the last couple of weeks, he’s talking about scrapping the whole thing. He said he’s concerned about the very large monthly payment when we also have to start thinking about a car for our son and him starting college in 2 years. I have to be honest, I’m a bit apprehensive about the payments, too. We can afford them but it will put a serious damper on being able to save for other things. The way things are going, I wouldn’t be surprised if we are separated by this time next week. I’ve always intended to stay in the house for a least a while after divorce, and he hates it and can’t wait to move (he begrudgingly agreed to wait until our son graduates HS but wanted us to immediately sell right after).

So my question is, is it smarter to just not do the home renovations? Or maybe just fix the roof and the rotting siding? We could maybe pay back this loan and get a smaller one with lower payments, I suppose.

My other question is, how do you tell your teen that you’re planning to separate and eventually divorce? He knows everything isn’t rainbows and unicorns but I definitely don’t think he’ll see it coming and that breaks my heart. 😢