With crate training, unless you are watching the pup 100%, he should be crated, in an xpen (or gated off area like the kitchen) This will help with potty training, not chewing on things he is not supposed to, and help avoid seperation anxiety later on. He needs to learn that being alone is okay.
I would never let a pup have free range of the house until he is 100% house trained (potty and chewing). So probably not until almost a year old or even older. Either crated/xpen or on a leash attached to you. This IMO is why people have so many problems with house training and destructive chewing. If your dog never has a chance to soil the rug, chew the couch, table legs, eat your underwear, your shoe, the tv remote, as a pup, he will never realize how fun it is.
I only give single ingredient treats, dehydrated liver, chicken jerky, etc and TINY treats, break them up into tiny pieces, if he has to chew it, its too big.
Keep training sessions short, 10-15 minutes max. If the pup loses interest stop. You want training sessions to be positive. Google positive reinforcement.
I am a fan of Leerburg, they have many free articles about training (I may not agree with all of their methods like, they dont like strangers petting their dogs, but it is very good) Leerburg Dog Training | Articles
I also like the book The Focused Puppy Leerburg | The Focused Puppy
Here's another website ClickerSolutions Training Articles Contents
I had no problems introducing multiple commands. Just go on how fast he learns. If he isnt getting it, move on to something else.
My pup learned sit, down, stay, shake, crawl, get your toy, bed, in the first few weeks.
Stay, speak, roll over, on your side didnt come until a few months later.