I suggest the you contact an air gun repair shop to have it fixed. Try looking up "Air gun repair" on the web and have them repair it for you.
The Colt 25 airsoft BB gun cost between $10 - $15 depending on the model.
Colt makes a 1911-A1 Pellet gun made by Umarex. I know of no BB gun unless you are asking about an Air Soft gun. The Pellet gun is very good. I can not answer about an Air soft gun.
About 100yd
Colt makes several different models. Which one are you asking about?
Not economically feasible.
Colt has 5 different model Air guns. The Defender is the only BB gun, the rest are pellet guns. Umarex makes all the airguns for colt. I suggest you contact UmarexUSA and ask them for assistance or repairs
The Colt 1911 A1 is rated at 395 FPS (Feet Per Second)
Leave it to a trained professional
You need to state the model and what is wrong with it.
Send it back to the manufacture or contact the manufacture to find out who repairs your BB gun.
As far as I know Gamo never made a bb gun named the FIX. They did make a model named the CFX, but it is a rifle and shoots pellets, it's not a bb gun. I suggest you contact Gamo at the link below and ask them.
If this is an Airsoft gun then 6MM BB's should fit.