There is absolutely nothing wrong with feeding in the snakes cage, cage aggression is an Internet myth. Most people on this site including myself feed in the snakes cage with 0 issues.
Once you get your thermostat you can get things rolling but until then you have no way to heat the snake safely so everything should be on hold until then.
As far as number of holes in the tub this varies greatly. The holes allow you to adjust the humidity in the tub. Someone who lives in Florida like me where the average humidity is just past unbearable will have to put more holes in their tub than someone who lives in Nevada will.