You'll spend a tad less making it 1x on the front. But you'll have to be real careful choosing what you get. Why not just fix or get new FDR and shifter? Are both truly broke requiring replacement of them?

Otherwise, it depends on how much you wish it to look like it was 1x from the start or how much you want to spend.

At the least expensive, you can just put it in the middle ring and go with that. You might take the big and small ring off, but the middle ring might depend on the other rings being there.

You can buy another crank for 1x, but then you have to learn about BB's, shaft diameter's and lengths, chain lines (maybe) and other things that might just bite you for your particular bike and replacement crank you picked.

2) Depends on what you have on the back. How strong you are. How you ride and how long you ride. What ring did you stay in the most for your previous rides on that bike? Did you need the smallest front regularly for anything you rode? Did you like pedaling down a hill in the middle ring?

3) No, but I used to own a 1x bike.