Welcome to YT!!
First off, potty outside will take time. Especially if you work all day. Try an expen and piddle pads for now, just to get him use to peeing and pooping in one place. He's older, so he can probably hold it. What you can do is take him for a long walk in the morning and as soon as you come home, and I mean 30-45 mins of walking. The exercise is good for Mr Biggs, and the more you walk, the more you stimulate the wanting to go. Keep the piddle pads out just in case. Mr Biggs is in a new home and that usually throws them off from their regular routines for a few days.
Get him neutered ASAP to help deter any bad marking habits. It's best to make sure his growth plates close (check with your vet) and if he's ready, when he's under for his neuter you can have any retained baby teeth pulled and have him microchipped for extra protection.
As for your other questions:
1. Kaji sleeps with me. Honestly, I wouldn't have it any other way. At first I was hesitant, and now that we downgraded to a smaller bed (twin sized) I got use to cuddling with him. Recently, I took him to Ross and he picked out his own bed. He would rather sleep there than with me!
2. As a rule of thumb, anything you find in the dog aisle at the grocery store is probably not good for your pup. It's all junk food. Try to find a more wholesome food, and most importantly something he will enjoy eating. When you do switch him over, do it slowly to avoid an upset tummy. Also, most fresh fruit and veggies make awesome treats! (and inexpensive)
3. I'm a little confused by this question. Do you want him to walk first, then have him potty?
4. Humping... that is totally normal. Male dogs will hump female dogs, male dogs, toys, beds; and females are exactly the same. It's not a sexual thing as much as it is dominance. If you want to teach him not to do it correct him every time he does it. Neutering him helps with this behavior as well.