In my opinion it seems he is going on the road to self-destruction.
You say that 'she' is everything he hates. He left a good 7 year relationship.
Could he be doing drugs, have a disease or tumor, received some really bad news that he cannot handle.... Maybe his plate is stuffed with so much crap that he is dwelling in trash on purpose.
People don't give up the good and go for the bad without a reason - you are not that reason or he would have told you. And, whatever it is, he is not willing or able at present to share it with anyone - hence - spending time with a 'brainless' warm body.
Unless and until he gets his life back to 'normal' don't let him drag you down to his level.
yeah, life sucks, but it should not stop you from setting new goals and achieving them.
Good luck dear.
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