I think you are not unique in having doubts about embarking on such a commitment as IOT and a future career in the RAF, and I remember before joining having concerns about some of the isolated locations and the demands of IOT. Throughout though, I had the enduring vision of flying military hardware, which provided more than sufficient motivation to counter my concerns and helped me get through the tough times of IOT.
Your concerns about not fitting-in are IMHO unfounded. A squadron, is made up of individuals, some of whom will be more socially gregarious than others, and since you have made it this far, someone has decided that you have sufficient social skills to be considered.
Whether or not the flying makes up for any or all of the downsides, is to an extent, up to you. I note that you have a preference for multis, but this may change as you go through flying training. It would be a shame to brush off the only opportunity you will ever have to fly high performance jets before you have had a taste of the more dynamic stages of training, and in any case, the training is set up to produce a FJ pilot. The other worthy specialisations normally stem from this format.
You have been offered an amazing opportunity but it's understandable that you want to make an informed decision. I'm slightly concerned that you mention a lot about what is to be gained, but given your talents and skills, you will be expected to lead, and that will require you to put others first. The training will help develop you as both a leader, and a good team member. If you consider these qualities to be "abstract ideals", then you need to reflect further, but if you consider that the assessment process has validated you as being worthy of this rare opportunity, then you should "pick up the gauntlet", give it your best, and enjoy the ride.