Really really really reinforce and reward his sit. If his default behaviour to get anything from us is to sit - you will slowly eliminate the jumping up at people, the counter surfing and generally rowdiness of lab puppies. In the initial stages also use management to prevent it happening, eg increase distance between him meeting people and have a lead on, do not leave him unsupervised in the kitchen to counter surf, or again have him in a pen so he can not jump up at the counters.
Ask him to sit for everything eg before he gets his food, before you stroke him, before you put his lead on, before he has any interaction with any thing. ask him to sit before you take his lead off, before he goes out to wee in the garden etc.
If he sits on his own without being asked reward him (use his daily food allowance for this.
To build up his wait , ask for a sit then a wait and as long as you give him a release command eg ok he should sit until you release him. Initially say ok really soon so he is only waiting for a mili second then build up.
Start all the training at home in a quiet place and then gradually take it into more exciting environments.
Loose lead walking requires commitment and consistency. Remember if he can not do it indoors he cant do it outside. If he cant walk to heel in the garden he will not do it on a walk.
The ideal situation is to exercise him in an area where it is safe to be off lead until lead walking is established but this is not always possible.
I lure heel work a lot with labs - they love their food and I constantly reward for being in the correct position. I reward at my side and give it a word. So initially just reward the dog for being at my side then when that is solid I add in movement so take a step and dog stay in position and gets rewarded and just increase the distance I can walk.
Some people prefer to turn around when the dog walks ahead _ I find this method frustrating for the dog and the me! but it works for many people.
Hang on in there with training he will get there