TBH I've kinda lost track of this thread after reading through it with all the replies and bitching back and forth. For what it's worth, here's my thoughts.
We had a Cockapoo which we took from someone who was ill treating it, we didn't want it, and I was working at the time so my wife took responsibility for it but she also took unwell not long after, resulting in me having to give up work and look after all the family. Because the dog pretty much was on the lowest scale as far as I was concerned, I wrongly concentrated on it last, I should have gave it up, but albeit as my wife's conditions stabilised I started taking the dog out for walks and she was a nightmare. Her anxieties and lack of socialising meant she became aggressive at other dogs, and would bark at people. She never bit anyone but would sound and look very aggressive.
As I tried more and more to socialise her, it did become a little easier and she did relax a tad more but for me, the breakthrough came when I bought an extending lead and trusted her with a little more freedom to approach other dogs and people. Some people would screw up their face and look down at me when she barked at them, but then I'd apologise and say she came from a bad home and we're socialising her, some appreciated it and we chatted about it, some just ignored me. I would be careful not to allow her near children, all be it we had small grandkids at the time which she loved, never showed aggression towards them and we always encouraged the kids to feed the dog and share tit bits with her, this gave her the pecking order and to this day she never barked at another kid even out in the street.
As I have her more freedom on the lead, I eventually got to the point where I could take her off the lead altogether and she would still go running towards other dogs but she would happily wag tails with them but she still never tolerated a male dog sniffing her rear end (she never had a litter), but this wasn't a massive issue.
Long story short, sometimes it's not necessarily about the training, it's more about socialising and allowing the dog to make their own mistakes. If you feel it really would be a big issue if the dog were to be trusted outside, make sure you give the dog a little bit of extra freedom with a much bigger dog, and if your dog decides to get nippy, it'll not be long before he/she realises other dogs bites and worse than their barks !!.
As for people interfering, there is nothing more decisive that talk. Get them round, explain how you feel, even if it is awkward, let them know you appreciate their help but only when you ask for it. If they put up a fight, it's time to close the door and let them know the next time they come over, it'll be invite only. You can't change some people, but you can change how they affect you. If you are 100% sure it's not you being selfish, then you're not doing anything wrong by talking to them and letting them know you feel put upon, but be careful they are not genuinely caring about you otherwise you may lose good friends/family. Talk, talk and talk, let them have their say, you have yours and if you can all agree, great, if not, it's time to make decisions.
Hope that ramble helps.