About the academic stuff, I might be wrong, but I'm getting the impression that your frustration at not getting the scores you know you could obtain (if everything else was working out) is actually hindering your scores. As in, by feeling depressed about not reaching the high standards you set for yourself, you get demotivated and score still lower. It's good to be ambitious and not want to scrape by, but not if that means you spend too much time on some subjects in an attempt to get A+'s there, while not doing enough for others that you then fail.

More generally, you have to ask yourself whether your pause from university wasn't too short. It was smart to do it, but it seems the issues that were making university difficult are still there to some extent. Especially since you don't really know what you want to study, anyway. Maybe getting a job for a year or two, in which you can feel proud of what you're achieving, might be good (after this semester, that is, do try to keep up the good work for this semester). Isaac's suggestions of volunteering and tutoring are also good ones. Taking a break from university in order to do better (perhaps in a different field) when you return to it later isn't failure, it's being wise. And contrary to what you seem to think, most people aren't really extraordinarily talented in anything. Perhaps it's easier for those that are, true, but the rest manages to get somewhere in life, too. As cliché as it may sound, the right mindset and hard work will usually get you further in life than just talent. You seem to be unduly harsh on your own talents, anyway - saying that you're nothing just because you're not the best at anything is not a helpful way of looking at things. This is why finding a position in which you can really make a difference for people - as a job or as a volunteering position - was a good suggestion.

And as for guilt, it can be a very debilitating emotion for people. Obviously you should be grateful to your parents, and appreciate the efforts they've made for you, and the hurt you've caused them. But you can't let that overwhelm you or impede your progress. You have to look forward, not backward, take the new chances given you. You can't change what is past, but you can do better now, if you don't let the past drag you back down. Dwelling on guilt too much is only going to lead to new things you'll have to feel guilty for, and will keep you in a negative spiral. So don't. Look at the positive signs, at the things you've achieved, even if it was less than you'd have wanted.

And finally about friendships or relationships - they are generally things that are easier to find if you're more relaxed about it and not looking too frantically. Obviously you have to go out of your way, step out of your comfort zone a bit perhaps, to make new friends or find a boyfriend, but much like the guilt thing, that will be easier to do if you don't keep dwelling on how you don't have any friends now, and how badly you want some. Have hobbies or activities for your own sake, things that you want to do (or don't really want to do but think you ought to) and if you meet people there, all the better; if not, it'll happen.