This is all hypothetical at the moment since you haven't yet been rejected from all 4 places. I do understand your torment though. Personally despite having done a degree, I feel a gap year would have done me the world of good leaving school, as a person if not necessarily for medicine. It is daunting though. You did well enough to get interviews which says academically you have what it takes to get to the interview stage.
Assuming you do well in your final year of school, applying again now would more likely result in an unconditional were you successful, takes the pressure off a bit at school. That is not a luxury available to you if you start a degree as you must finish and the bench mark is moved each year so it could be a 2:1 or a 1st. Even just taking the time to do the UKCAT again will give you a good idea of where you stand for next year, plus if you do it early you may still be in time for clearing through UCAS at the universities if you don't think you did well enough to give the application process another go at that point.
Extroverted and humorous doesn't necessarily spell good medic. There are other qualities you need to explore in yourself. A gap year will help you do that. I found experiences like Camp America and Volunteering really opened up my eyes to the person I was and how I could improve myself, experiences which I don't think I would be in the position I am in without. They also make GREAT talking points at interview. Pretty sure all I talked about was Guide Dogs and Camp America, and because they are so real and mean so much, passion comes across much better. They tend to be more unique to you and that comes across. Everyone does Duke of Edinburgh because its a good thing to do, but not many people choose these experiences for themselves and organise them themselves.
Get all the feedback you can from any and all interviews. There will probably be one or two particular things that held you back. If you feel those are things you can work on before interviews in Nov/Dec then go for it! I didn't go on interview course but read two interview books, one on interviews and one on ethics, and practiced over and over and over and over (you get the idea) with each person, until they literally can't stand the sight of you. You'd think I'd run out of questions but when you come across the same question, answer it differently and see what reaction you get to each, note it down. choose which gets the best response. Family and friends might not be doctors or med students but they are the members of the public you would be treating so they will have some idea of how they would like to be treated.
Having said this, if you apply again next year and didn't get in, I would seriously consider taking a degree in something that interests you other than medicine. Related degrees are inherently useful and the university experience will help you when it comes to doing it post-degree. You would be far from alone. Pretty sure half my course has applied! University is great for shaping you as a person, building independence, experiencing new sports and hobbies you would never have considered and of course learning about something that you might enjoy/find useful. It is by no means a waste of your time. Of course we would all love to walk straight into medicine but for a lot of people it doesn't work like that. Some of our lecturers think that we should have a similar system to the US where you have to do a degree before medicine because it really helps you consider if it is right for you and helps you mature (without the extortionate fees).
I think it is naive to apply over and over again, I would say 3-4 times is probably the maximum you should spend applying because at that point you should probably consider what it is that doesn't make you right for medicine that makes you great for something else (own personal opinion). It's great to have passion but it also good to recognise strengths and weaknesses and where you can apply them. You might discover something great. However applying twice is more than common and you should definitely go for it if you still feel medicine is what you are game for! You will not be alone and you never know what you might discover in yourself. Sorry for the essay but hope this helps you weigh it all up