All I can suggest is that you ask your friends to help you teach him not to bite or nibble on them, and see if they'll come over or if you can take him there a few times a week specifically for practice. Ask them to ignore, get up and walk away, not even look or speak to him when he does that...give NO payoff what so ever. Then the minute he stops biting or nibbling, ask them to pat and praise him and give him a treat. Does he know sit, stay etc? When you or your friends see him coming and he looks like he's in that mood for biting, nibbling, BEFORE he does, ask him to sit or down. Give him something else to do and praise him for that. Sometimes giving an alternative "job" gets their mind on something else and makes them feel like they have something important to do now...no time for silly business.
With the jumping, I'd do basically the same thing. Ask your guests to brace themselves and turn away and ABSOLUTELY ignore the dog. If they can catch it before he jumps up, they can ask him to sit/praise and then go down to his level and pat him. What I did sometimes is to squat down a little (MAKE SURE YOU DO THIS WHEN THE DOG IS NOT JUMPING, BEFORE HE JUMPS....don't reward for jumping) and situate the dog broadside (sideways) in front of me. They're not as apt or able to jump up if they're sideways... and you kind of get the dog closely tucked into you...kind of hold him there and pat and coo or whatever. They find out that they'll get attention when they stay on all fours, but won't get ANY if they jump up.
I'd also...just in general, beef up the obedience skills and give this dog something more constructive to think about and do. Make sure he's getting plenty of exercise so he's a little tired when you are going to practice. He'll be more apt to be successful. And the more successes he has and fun/praise for that behavior, the sooner he'll learn. The more he continues to do this, the more it will become habit and harder to undo. He'll settle down in time. But it sometimes is needed, to actually practice with the situation he's really having the trouble with....ie: your friends.
Anyhow, hope some of that will help.