converting old bike into singlespeed: how to deal with those issues?

Hi everyone!

Doing it yourself for the first time so some questions might be very obvious

1. I’m looking for a crankset that fits my bottom bracket. It’s 1.37x24t standard. I tried to google all variations and I’m completely lost. What should I look for and which parameters matter so everything fits together?

2. My fork appears to be damaged. I can’t screw a little thingy on top of it. Is it possible to repair/cut it off? Or is it better to find a replacement? My bike is made from ishiwata 022 steel and it’s kinda lightweight