House Training

When I brought home a 1yo (now about 16 mos) lab/springer mix from a rescue place 3 months ago I'd get up every 90 mins through the night to let him out to toilet. After about 3 weeks I found I could leave it longer before taking him out, every 3 hrs. However in the last 6-8 weeks he has been forgetting himself and will pee on floor. I am back to bringing him out every 2 hrs during the day and night. He will pee outside etc but only if I go out and stand with him. I thought it'd only happen the first couple weeks cos he was getting used to new surroundings but he still does it 3 months later.

He was on the sofa a few mins ago and I went over to wipe his nose and he peed as I done it. He has also started what I think is called submissive urination, I tried to give him a helping hand going out to toilet by pushing him gently from the back but this started the submissive peeing and now it happens even when I hold him by the collar.

He is a very clingy dog, he cries if he can't see me. If I go out to the shop he will take something of mine and destroy it. About 2 weeks ago I started leaving him out the back for a few hrs every day to separate us and sometimes he is ok with it and sometimes not. He will howl looking back in.

I totally love him and i want him to be a secure and happy dog, has anyone any suggestions?