Need help housetraining and separation anxiety with my dog

I'm new to this forum. I adopted a 3 month old fox terrier from the shelter who is now 4 months old(had him for approximately 1 month). The vets said he will be around 10 to 12 lbs when he is full grown. He is the cutest thing EVER but we have 2 MAJOR problems.

We have read countless articles on how to train our dog on pee pads and reducing separation anxiety. I feel like I have tried almost everything but then when I turn our back on our puppy, he pees on the carpet and off the pee pad and howls like there's no tomorrow when we leave HIS SIGHT. I believe my dog was heavily abused before he went into the shelter. He is very scared of older males(people) and barks at them where ever I go. He is extremely squirmish and looks like hes gonna have a heartache when I slightly raise my voice. When I raise my voice and go to pick him up, there's yet another pile of pee where he was grounded at. I swear, it's like whenever I tell him "NO", or praise him with treats when he actually goes on the pee pad, like he forgets where to go the next time he pees.

For the separation anxiety it's worse. He howls and cries so much when I leave his sight. Theres like no end to his crying. I never pick him up and stuff if he cries and stuff because I dont want more problems. I have to literally take him everywhere I go. I live in an apartment so two or three notices and I could get evicted.

Honestly, it's not like I'm through with him. I still want to try new things to see a modest improvement but if I don't see anymore improving in a month, I don't think I can keep him any longer. I have crate trained him. He likes the crate and all but he just doesn't know where to go. PLEASE HELPPPP