Will #2 aluminum wire fit a 100 amp cutler - hammer circuit breaker

Look up the breaker on Cutler hammer's site.

www.letmegooglethatforyou.com

I would so appreciate it if you could do that cause I haven't been able to find the specs for the 100 amp main breaker

Do you have the panel number or breaker number?

http://www.eaton.com/ecm/idcplg?IdcService=GET_FILE&dID=151312

I believe the Model # is BR2100

p55 in the reference I gave you: #4 to 1/0 Cu/Al; so the answer is yes for #2.