I too am puzzled by the erratic behavior of your TT Pro .46; to the best of my knowledge, there never has been a "bad batch" of this engine from Thunder Tiger. The Pro .46 is famous for easy starting and incredible reliability. The TT Pro .46 isn't particularly sensitive toward fuel or glow plug type, and the props you've been using are all within a comfortable range for the engine to turn. Any modern 10% to 15% nitro sport fuel should work well in a TT Pro .46, as should most any long medium-to-hot glow plug (with or without idle bar).

It doesn't sound like you're chasing an air leak to me, that usually manifests itself as erratic tuning rather than being hard to start. Most "engine" problems actually turn out to be plumbing/fuel tank related. Pulling your tank and inspecting your clunk setup and fuel lines could save you considerable time and frustration. Installing fresh fuel lines is inexpensive and will often clear up "engine trouble" even if you can't see exactly what the problem is on initial inspection.

It also wouldn't be a bad idea to try flushing out your needle valve assembly by pumping fuel through it backward to flush out anything that might be caught in it. A bit of gunk in the needle valve assembly can cause the kinds of intermittent run/start issues you're describing.

If you go through the fuel tank and plumbing thoroughly and you flush out the carburetor and you're still not getting reliable performance from your TT Pro .46, see if somebody else in your club could break it down and inspect the cylinder, liner, and bearings for you. Thunder Tiger Pro .46s want to run, and when they run they generally don't quit until simply run out of fuel. They're so reliable and so easy to start, that I use one on my Sea Master specifically for dead solid reliability when float flying.

Even though the engine might look lightly used, yours isn't running like it should. Your rpms are a bit lower than expected. If it isn't a fuel or plumbing problem, then it might be in need of a couple of replacement parts.