no problems,
any esc that can handle 7.2v will handle a 7.4v lipo. I run 7.4v lipos on my tamiya teu 101bks all the time.
As to a NA store that sells the TRF416....
http://www3.towerhobbies.com/cgi-bin...?&I=LXWCP1&P=7
When you're considering the weight, take into account the battery mah... a higher mah capacity battery will weight more.
BTW, that maxamps pack is not roar approved. it's not a hard cased lipo, just a thick plastic shrink wrap.
Take a look at
http://www3.towerhobbies.com/cgi-bin...&I=LXUYY4&P=SM
http://www3.towerhobbies.com/cgi-bin...&I=LXVSS5&P=SM
As for your charger, why buy another when you have one that works? Just download the manual. The hyperion is a good charger but for hard cased lipos like I linked to you need a special harness or balancer like this one.
http://www3.towerhobbies.com/cgi-bin...?&I=LXRWF8&P=M