Sorry you are going through this. It’s really sad when someone disrupts the balance in a good dynamic. It’s worse when its a parent as you feel obligated. Just try and remember the good things. Yes he was strict but maybe that gave you the discipline to work harder compared to others who lack motivation and cant get their life together. Also even though he didnt really want to, he did help you getting to USA which you now love living there. Also in regards to his lady friend, if your culture was more open to divorce maybe he wouldve divorced and moved on and your mum too. But when divorce isnt an option then things like this can happen unfortunately. If he cones to live with you, you will just have to stand your ground. He is coming into your territory now and he has to respect your rules. As parents age they become like babies and you have to assert your authority. Just remember when he eventually passes you wont remember any of this. Especially if he passes overseas alone you will only remember that he died alone. So just do your bit and try your best.