OP you handled it fine though personally I wouldn't have talked to the idiot and went to the FA first.
Thankfully I've only had to deal with a persistent seat-kicker once. It started as soon as the engines spooled up for the take off roll out of ORD to PHX. I figured she was just nervous or a bit scared so I ignored it until finally about 20 minutes into the flight I turned around and politely said "You're not going to kick my seat all the way to Phoenix are you?" Thankfully her mom gave her the "knock it of NOW!" look and that ended it.