1. I'll simply say no, the upgrade is not necessary at all, it is you're only choice to make, I seem to love 6.5 more though, you can always try a custom ROM though! trust me you will love those.
2. I can tell you that you don't need to flash to new 6.5 ROM but I'm not sure if you need to unlock the TP2 for it... you can just flash to the new ROM though, as it is considered the new "stock" ROM. then you can flash to any other ROM or the old sprint 6.1 ROM.
you can download the radio via this link than try updating to it
ftp://up.ppcgeeks.com/Touch%20Pro%20...int_2.32WF.exe