Well, a lot of that is pretty confusing. The "till it's level" was referring to the model, or the stab but a bubble level really isnt required, the good old mark one eyeball will work fine. Establishing where it should be balanced has nothing to do with checking the CG with the V rig. The rig tells you where it is balanced and you need to know where to put the weight to bring it to where the "where it should be calculations" have indicated. The support harness (ropes, cords, nylon strap whatever) should not slip around on the model so something needs to be done about that. The rod (large dowel/broom handle) needs to be large enough to provide traction for the "wraps" of the harness, a length of music wire isnt a good choice for the rod. It needs to provide a stable surface for the cords. The rig your Puppeteer is dangling from looks suitable, I'd prefer a larger dowel but that one will prolly work. And yes with 5 degrees of positive incidence in the stab and lower wing the SE 5a fuse needs to be at least 5 degrees nose down, that's a no brainer.
If the axle of the LG is near the CG it (the model) doesnt have to tip very far fwd to put the CG ahead of the axle and at that point you better have enough airspeed so your elevator can control it or its a prop strike. Both scales of my N28s are sensitive to this as the gear on both models is scale in dimension, location and function. Wheel landings need to be done at a slow enough speed so elevator can be used to keep the tail down without the model flying up again. So check Chris' recommendation on CG and do a little math and see where 25% of MAC is and compare and maybe do some adjusting if it looks like it could be a bit further back. All the calculations are is a starting point anyway as eack model will likely differ somewhat from another, flying it is what tells you if the CG is OK/
Doc