Hi, I know where you are coming from on this. I have hated flying (at times) for this very reason. I have previously had to ask for a seatbelt extender, sometimes the staff are discreet and other times they have tried to milk the maximum embarrassment out of it. I just try not to let it get to me.
I have just come back from a European holiday, flight of 3 hours 45 minutes and I didn't use a seat belt extender, but the seat belt had to go under my tummy and was quite tight and uncomfortable - but it did do up. If you are travelling with family it is not too bad as you can sit next to them, the arm doesn't need to go all the way down (mine just rested on my leg) and if you sit next to the window you get a bit of extra room. As for the table coming down, if it doesn't go down all the way I just don't use it and put things on my partners table. With short haul flights these days you don't usually have a full tray meal, so it doesn't really matter.
I agree with the toilets, I avoid them if at all possible. It isn't a problem to get in, but I have found before that I have had trouble bending down to pick up trousers as there just hasn't been enough room in between the toilet and the door! The exception to that has been on longhaul when there was one disabled toilet on board - that was the one that had the longest queue as there was enough room to move around in it!
I really wouldn't be put off going on holiday. Just be prepared to ask for a belt extender if needed, (or research which airline you are on and you can buy them online - there are different fittings so you do need to check which is the right one).
What I hate is flying on my own, I flew to America about 6 years ago now and I was so paranoid that I booked two seats - yep that's right, I paid for two seats - apparently if you book a 2nd seat you don't pay the tax so it was cheaper than booking premium economy to book two seats. It was comfortable but it caused no end of problems on the internal American flight as they couldn't understand why I had two boarding passes!
On the flight back to the UK, the seat configuration was 2 seats by the window, 4 in the middle and 2 by the window. I had prebooked the two seats by the window and was harassed constantly by people from the middle of the row of 4 seats wanting to move into one of my seats - even though I explained that I had paid for 2 seats. Even the air stewards asked me to allow someone to move into the 2nd seat to be near to their child & other half. I refused and it didn't go down well! They just didn't understand! What was meant to make things less stressful just made things worse!
These are some of the reasons I am looking into WLS. I just want to get on a flight, or walk into a restaurant without the stress of "is there a chair without arms that I can fit into" " will the seatbelt do up". Amongst other reasons of course.......