Addressing the jumping issue... I'm currently working with a friend and her 3 yr old dog, who is going thru a similar jumping issue. I know we (as people) tend to try to be polite, and love when people like our dogs and want to pet them. I think in this case, you need to be firm with the *potentially* offending people, and when your little yorkie goes running up to someone and jumps on them (and you know the next thing coming is "it's ok" then the pet-fest begins), you need to say (and mean it) please ignore my dog if he jumps on you - he's in training and is not to be petted unless all 4 are on the floor. And don't take no for an answer. Really mean it, and enforce it. If the petting has already begun, then take Buddha away, and approach again - this time, with people being forwarned. When Buddha realizes he gets nothing out of jumping on people, just no reward at all, it will stop. Ask the people (and you too) to not look at him, not to talk to him, and don't pet him. And when all 4 stay on the floor, let the pet-fest begin. And if the jumping starts - immediately withdraw all attention - meaning, don't talk to him, don't even look at him. Wait him out, til again, all 4 are on the floor and he's calm. He's jumping because he's being rewarded for it every single time. Dogs do what works for them. If the rewards cease, so will the jumping - what would be the point? He'll get it, and most likely, he'll get it quickly. Dogs are masters of body language. When there's no payoff for jumping anymore, but the big payoff comes when he sits and looks up with those adorable eyes, bingo!
As for the furniture - is he allowed on the furniture when you are home? You didn't say, so I'm wondering if he is. And, does he try to get on furniture you don't want him on when you're home - and if so, how do you handle it then? Since you didn't say (and pardon me, because I don't know what training he's had) he might just need some basic training, basic rules: one being "off". He jumps up on the couch, you actually reward him for getting "off" - goooood boy!! He jumps back up, OFF - (throw reward on floor), gooood boy!! About a zillion times - and he learns good stuff happens when I'm on the floor, not the furniture - I'll stay on the floor.
And as for the potty issue, that's a tough one. First question - are you being very diligent about cleaning up all his potty with an enzymatic cleaner, such as Nature's Miracle? If it's being cleaned up, but the smell is still around, he'll continue to go - forever. If there's any question, I'd start there, get some enzymatic cleaner, and clean anywhere he possibly could have gone, really really good. Then, I'd start him all over just like a puppy - take him out to potty, ask him to go (whatever word you choose) and make a HUGE deal when he goes, throw a party, treats, make it just so much fun! I'd do that every single time you take him out for a while, weeks, and I'd take him out every hour or two, so he catches on to the whole "potty outside" idea. I'd also rethink how long you're leaving him at home. I'd do like Reveuse suggested above - leave him for 30 min, then 1 hour - see if he goes inside. If that's ok, then try 90 min - if that's too long, then step back. Set him up for success - find out what his "potty threshold" is - at least for now (and apparently it's different while you're gone, than in the middle of the night). Give him time to work up. Also, are you sure he's pottying before you leave? Do you ever take him out for a long walk and let him "empty out" before you leave? Asking a male dog to go out and potty can be tricky - he might quickly mark, then come inside and once you're gone, and he's trapped inside, really have to go. I'm only asking some of these questions, because I know sometimes when we get caught in the middle of dog issues, we get so entrenched in trying to solve them, we can overlook obvious things. Forgive me if I've asked questions or made suggestions that seem ridiculous. Patricia McConnell has a booklet entitled "Way to Go! How to Housetrain a Dog of Any Age" - you may find some hints in it that could help you, as it's not geared strictly for puppies.
I'm sure someone else will chime in with more suggestions. Good luck, keep us posted!