He looks normal to me. I agree, you don't need to diet or do more cardio (but you should be doing some, just to stay healthy).
Strength training is good for you, for lots of reasons not just to build muscle. I think you should try this for a few months & see what happens. Haven't you guys seen those before/after photos of teenagers who do Basic Training? Of course a proper strength training program can help.
Just find someone who knows what they are about. Don't ask the local gym monkey, chances are you'll be hurt. Get some books out of the library, or ask a certified trainer (with a degree from a college you've heard of) if you can do some work with them for a few hours.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh