Don't over think the process. It's easy to get caught up in complicated arrangements when a simple solution will work. I've mounted servos about every which way possible, as long as you've got a straight shot to your control horn you'll be fine. BTW, I've used all kinds of wire for pushrods. Doesn't have to be "push-rods" from the store. The wire flags you buy from the hardware store work great.
And not to reinterate, but go as big as you can with you're plane. The more surface area you have the more forgiving it'll be with weight. My guinea has 9g metal servos on the tail (had I mean) but the wing is massive so the weight wasn't an issue.
Thin ply, thick plastic, plexi glass, all work great. I'd steer clear of softer woods and foam for sure. Also, you'll want the motor to have a slight right/down angle. I usually just washer the top and left side when screwing the motor down.
Here is a really important thing for your control linkage setup. The control horn attached to the control surface should align with the hinge line. (Please ignore some of the other specific details in this drawing, you aren't doing a pull / spring system, but the control horn alignment is the important thing to notice.) Based on your picture, your rudder will have very little motion. I can't see your elevator setup. Also, if you ever do a swept wing, make sure the pushrod and control horn are perpendicular to the hinge line (as seen from a top down view.) Hope that helps.
Here is one very important thing I haven't seen mentioned here: angling the motor slightly down and to the right only applies to motors that spin counterclockwise when viewed from the front. This is to reduce torque related issues, and so, if you angle a clockwise spinning motor down and to the right, you will get even worse torque issues. I made this mistake on my first plane, and I couldn't even get it in the air before it was destroyed. For a clockwise spinning motor, angle it down and to the left, and you should be fine.
There ya go! She's got a much more proportional shape to her now. I can't seem to make out how you did your elevator horn from the first pic. Now, this is just from experience. But sometimes, especially when you're improving a design, you might have to start over just due to weight. I've ditched more than my share of wings just because they were 45% hot glue. You've made some great design improvements, and you should start seeing some much better glide test out of it now too.
Only one question, what are you cutting your foam board with?
Keep it up!
Just curious, it looks like it's trying to snag the paper when your cutting. I'm notorious for using a knife way after it's dull. Just don't let a dull knife frustrate you. Have you pinpointed where to balance her yet? I usually cut a piece of paper the width of the wing and fold it into thirds. Lay the paper over your wing and mark the first fold line. That'll be 33% of the cord and should get you close to balance. Looks like she's ready for another glide test!