I cannot understand why you are threatening to quit so close to the skills test just because your instructor says your knowledge is lacking. Ask another instructor to quiz you and if he says the same maybe your knowledge is lacking and you need to get the books out some more.
As you sure you are not just nervous about the skills test and looking for an excuse to quit. You can then go back to your family and say "I really wanted to fly all my life but this big bad instructor upset me just before my skills test and now I am going to quit".
You are 36 for gawds sake,
Fly with another instructor - no big deal.
Introduce yourself to all the staff and then make an effort to pass the time of day with them. Phone up before-hand to ensure the lesson is going ahead.
I was lucky in my training in that I had 2 instructors from start to finish and I got on really well with both of them but I wouldn't have gave it a second thought to "sack" one of them if they made me feel uncomfortable.
I think you hit the nail on the head with your statement about not wanting it enough.
Quit now and I can guarantee you will regret it for the rest of your life.
Become a PPL and I can guarantee that you will feel a sense of achievement and you will bore everyone silly with the fact that you can fly a plane.
Don't let a tw*t of an instructor stop you....unless of course you ARE using this as an excuse to quit.
28th,,