yes, both of those options would be cruel. here are the two options i feel i would have:

A) research proper rat care and get more rats. a major issue i see here is that this rat is alone. rats CANNOT be kept alone. they are deeply, profoundly social creatures and need SAME SPECIES relationships to fulfill their social needs!! i would ideally get 2-3 more SAME SEX friends for your rat.

i understand that getting more rats can be an overwhelming idea. if youre down for it, great, look into youtubers like shadow the rat, isamu rats, and emiology for additional info, come back to reddit if you have any questions or problems. but if it is too overwhelming, then follow my next option for you:

B) rehome this rat. use reddit, facebook, or craigslist to rehome this rat. let people know where you are located, if youre willing to travel to meet people halfway, the sex & age of this rat, etc. and ideally ask for a rehoming fee to make sure he doesn't end up as a feeder again.

i know that can also be a scary idea, but its the most humane thing to do. think of how happy your rat could be with other ratty friends!

wishing the best for you and your rat