but I dont want to make the wrong decision for my children
Ok, it sounds like you're twisting yourself up trying to make a perfect decision (which does not exist), so look at it like this: what is the least bad path?
Staying like this in a stressful atmosphere learning unhealthy behaviours?
Growing up in a relaxed atmosphere learning healthy behaviours?
What's the part that's tripping you up - the media / society narrative that single mothers are raising their children in "broken homes" ?
but then there's all the arrangements and decisions that come with splitting up that I just can't get my around.
You don't have to do it all at once and it would be better not to try - that's what's overwhelming you.
As with anything daunting and complicated, you take it one step and one element at a time. One step then another then another.
It's perfectly manageable taken like that.
Use reliable information sources - you can get good advice on Mumsnet but sometimes people repeat things they wish were true or heard down the pub that are legally or factually incorrect.
Citizens Advice has very good information pages on lots of topics including divorce, child arrangements, finances etc. They are easy to read.
Money Advice Service and Money Saving Expert have reliable financial information.
Entitledto can help you consider where you stand with social security.
If you are looking at therapy, make sure they are qualified and regulated - BACP, HCPC.
You can also search for therapists on Bupa's website, which might give you a sense of things to think about in terms of qualifications and specialisms. Obviously that limits your pool to only those with a contract to Bupa but it could be helpful as a starting point. Other private healthcare providers may have the same available, this is just one I happen to know about.
The usual advice is to interview a few therapists before picking the best fit. Don't just go with the first one you find - much of therapy is about the therapeutic relationship so it needs to be the right fit.