RE: First electric plane.
The Himaxx 2025 is rated for 175Watts. With electric planes, a general guide is to compare the weight of the plane by how many watts the motor system can provide as watts is the amount of work being produced.
I think "Sport" performance is somewhere around 50 watts per pound, which is likely where you'll end up with, likely more.
I'm not too sure about your batteries, what are they exactly, 3 cell lipos?
If they are 3 cell Lipos (11.1V), I'd bet you could go up to a 12 x 6.
If no one else pipes in on the servo question, the smallest servo I'd go for in that plane would be a something like a Hitec HS-81. In slow flight, I would be confident the HS55's could handle it, but I'd be concerned that if I built up too much speed (like in a dive) the HS55's might not.