First of all... breathe.
It is a huge change, and is understandably going to bring all these worries.
First one... If you don't feel any better in yourself (don't know any of your history, sorry , so don't know if it is mentally or physically) then I would say that work isn't the underlying cause, and it will give you another angle to look at things at iyswim... kind of like elimination diets.
House still a bombsite - are you stopping work to clean, or to spend time with your boys before school? To my mind the house is always a second place thing - if it gets and stays clean, it is a bonus, but the mum thing is more important.
Boys don't get as much out of life - they will get their mum, something they can't get from a childminder. They will still have their 2 days a week wherever they are too I am assuming...
DS2 being clingy - I get the feeling if they are gonna be clingy, then they'll be clingy whatever . It could be that by having you around more, it lessens.
If you don't have enough money - economise, or if all else fails and it really goes wrong, then increase your hours again. As long as you keep on top of it and are sensible, then a smaller budget is doable - just make sure that you know where everything is and needs to be at all times, so that you don't suddenly look one day and realise that the hole is too big to get out of.
DH resenting you - Talk to him! I know that my DH would love to be home more, but at the end of the day, he knows equally how miserable I would be away from DD, and my miserable is more acute than his "it'd be nice" iyswim. Luckily I am married to a man who doesn't see mess , so we don't have a whole "what have you been doing all day" thing - the one thing to have changed since I became full time SAHM is that he never cooks anymore (before it was shared), and he seems to appreciate that.
I don't know if any of that helped - just really things as I saw them.