On average I play opponents about 100 points stronger than myself. Is it possible my rating is undervalued because I'm not playing the easier games and missing out on points. Or has this been accounted for in the mystical ratings formulae?

I just want some stronger opponents!

It is accounted for. In general when you play higher rated players you gain more rating points for a win or draw and lose less for a loss. So in the end even if you win or draw few games your rating is fine.

Conversely playing lower rated opponents is risky as you could lose many points for little reward when you win. (Zero rating points for a win if the difference is big enough.)

You can see this in the behaviour of highly rated professionals. They play round robin tournaments with each other, rather than risk losing major points in open Swiss style tournaments if they have a bad day or happen to play an upcoming underrated prodigy. 

 I think you have misunderstood; my point is the differences in rating points awarded seem to be disproporionate. I could easily pick up 5 or so points playing weaker players but only get 20 for doing the impossible. 

 I'm sure it would take a more skilled player to win that 1 hard game instead of a few easy ones

To get better, play people within 100 points of your rating (higher or lower) and you will quickly improve.