Yeah, I'm pretty sure the broken fuselage is probably the cause of ALL your problems. You can't reasonably expect a broken plane to perform like a whole plane. Fixing or replacing the fuselage stick is the best course of action at this point.

Until you can fly the Slo-V with confidence, I wouldn't even consider a Stryker if I were you. The Stryker is much heavier, much faster, and much more responsive. At this stage of the game I'm afraid all it'll do is crash faster and break quicker...

As far as fixing the stick, I am not familiar enough with the Slo-V to tell you what you can/should do. Maybe you can find a wooden dowel to shove down it to stiffen it up? That won't work if the pull cords for the tail flaps run inside the fuselage. Part of this hobby is being creative and finding creative, effective ways of repairing broken planes. Sometimes you need a new part, and that may be the case this time.