For me the cost is too high - both financial and emotional.
He WILL bring OW into the house. I couldn't stand that.
How long would you be able to do it for? Could you honestly see yourself renting a room on your 'off' time. You would be permanently off-kilter. Like you were banished from your own home during 'his' time.
You will have far too much to do with him. Laundry, groceries, cleaning, bills etc. It will be like living with the ghost of your dead husband.
You will be stuck in limbo hell. The only thing worse than what you describe would be in-house separation and that is only marginally worse.
You're trying to delay the inevitable. You're trying to gain some control of this out of control situation. You're trying to protect your kids and not put them through too much change. I get it. Your intentions are good but the cost is too great and I don't the perceived benefit to them is worth the huge personal toll it will take on you.
We sold the marital home and I moved into an rented apartment. It is all mine and the girls and I have been very happy here. They were excited about their new home and I didn't have to live with horrible triggers. I cannot tell you how amazing it has been having my little sanctuary.
Your kids don't want/need the house. They need their mum to be OK. IMHO there is little to no chance of this arrangement equalling you being OK.
50/50 killed me in the beginning too. It has been a year now and I can say the only upside of 50/50 was that in the early days I could be a hot mess on the floor on the days I didn't have them. It also means I get some 'me' time. Far more than I want or need but still, I do have it.
Nowadays I use that time to get all of the housework done so its 100% mummy time when they are home. I spend more quality time with them now than I ever did during the M. I am happier, more relaxed, patient and giving. Mostly because I am no longer in that vice of a relationship.
I still feel like the other 50% is stolen from me for him to squander by not having quality time with them but there is nothing I can do about it except make the best of the precious time I do have.
I cried a river when I closed the door on that house for the last time. It was one of the hardest times of my life but it also set me free. I don't miss the house - I also no longer miss the hopes and dreams I held in that house.
I now have new hopes, new dreams and they are attainable.
Your kids will be OK if you are OK.