Could you tell me if it is a good choise continuing this project with PIC16f887
its basically the same very limited chip you are presently using with a few more pins.
if you are serious in wanting to calculate maidenhead then no its a poor choice.
at least get something like 16f18326 ,16f18875 or better still a pic18 chip
I like pic18f26k42 [if you have pbp3.1] or a pic18f26k22 with pbp3.0 for this sort of project