You should be fine putting on a 1.75. There is typically enough clearance to accommodate a small jump in thickness. If you were jumping from a 1.5 to a 2.2 then we would suggest to bring it in to the shop so we can verify if it will clear your fork/seat stay 👍
The tire will fit on the rim no problem. The only issue could be frame clearance. If you're getting a knobby tire remember to allow room for the knobs to clear the frame or fork.
Depends on the width of the front fork and fenders if it has fenders.
First of all, I don't know the straight answer. Personally, I would do it. You're only dealing with a one-quarter inch difference in tire width. Very hard to see how the bead would not seat every bit as solidly as the 1.5 tire.
Thanks! Your answer is awaiting moderation.