It's no problem, but you shoud remain the same Tm value for these two primers 

It's no problem, but you shoud remain the same Tm value for these two primers 

No problem. It's not necessary for primers forward and reverse have the same lenght. 

Some useful guide for PCR primer design:

http://www.premierbiosoft.com/tech_notes/PCR_Primer_Design.html

Tm value of both the primers should be +/- 2, will work perfectly with your PCR.

There is no reason  to avoid different primer lengths

Yes, you can use primers that have different lenghts

Absolutely no reason for not using a  primer set having different lengths as long as their Tms dont vary much

Yes, not an issue