5.1 should be ok, just dont rely on it try not to pump overvoltage down it. Anything above 5v can damage the PIC, but it should be able to cope with this little extra. best solution is get a zener less than 5v. doesnt have to be exact, but under is better than over always.
0.1" standard connectors as used on almost all mobos. keep in mind we sell bare wires or femaleconnectors to female for the connections.
the timers split the program into 4 sections. However IO is 1 timer. every time the Brain is polled the full packet is sent back and forth. so only evaluating 1 input of the bunch is a waste.