A classic problem with a sideways mounted Fox 35 (like on a profile) is the cut-out when going inverted. Turns out, the tank really needs to be higher than the thrust line, by about 5/16". This means that inverted, the tank will be slightly lower and the famous Fox "burp" should disappear. Or, you could try a clunk tank - it is far less critical.

Sounds like you got the engine straight up and down, which will solve the whole problem.

For an outside wing listing up, you need to check a few things. Is the wing up when inverted, too? If so, then it's too little tip weight - add some. If the wing is down in inverted flight, then there's either a warp, or the flaps are not straight. Warps are easy if it's monokote - just flex the wing in the opposite direction, and iron out the wrinkles. A fabric covered wing will sometimes respond to steaming over a pot of boiling water. Flaps can be fixed by bending the flap horn, but try to clamp something on the flaps to spread the load if you try to twist them - otherwise, you can break the flaps off. If all that fails, you can still try a trim tab. Epoxy a short strip of sheet aluminum on the outside trailing edge. You can bend it and it will retain its shape.

Good luck.