Craig Allen
Finally riding a big boys bike
For the loose cranks, you probably have a situation where the crank keys are just barely engaging the middle of the axle which allows the crank to rock back and forth. You can build up the crank axle slots with a little brazing and carefully file to correct this. Use a Dremel tool to grind off just some of the surface metal in the slots to ensure a good brazing knit. You can also try making new crank keys with less of a taper. Since you said you are not going to do much riding on this bike, this is a quick fix without materially altering anything.