Don't worry so much, you're doing just fine
I have to admit, I was the same as you when my son was that age, but different concerns.......should I give him his bottle first, or jarred food first, is he getting enough formula a day, will he ever hold his own bottle, etc, etc.
If your son is healthy, and gaining a good amt of weight (according to what his doctor says at checkups), then I wouldn't worry too much.
Use his cues as your guideline for feeding him. If he seems hungry try offering him a jar of baby food or bottle. If he only has a few teaspoons of jarred food, then that's ok.
With the sippy cup, I just tried it one day with his meals. At first he would just chew on the spout, and eventually he learned to suck from it to drink.
I always offered a sippy cup of milk (at 1 yr) with his meals, and in between meals water, and not juice. That way he is not filling up on juice.
Make sure you are not giving him too much juice because that will definitely fill him up and he will not eat as much jarred food and get the nutrients he needs. If you do give him juice, get the unsweetened or water down the regular juice with water.
Oh, yeah and don't forget to wipe his teeth and gums with a clean wet cloth to prevent decay