On your engine starting issue ...
How do you fill the tank? Do you pull the line off the engine and fill on that pulled line? Or is there a separate connection to fill from, that you plug up later? Or ... is there a fancy "fueler" between the tank and the engine?
The reason I ask these questions is that if the engine suction line is attached to the engine while you are fueling, and the tank is high, then it is possible to fill the crankcase of the engine before the tank gets completely filled. However, if you have only two lines coming off the tank, and you use the one that goes to the engine to fill with, then this is not the problem with possible flooding of your engine.
Just because fuel does not come out the glow plug hole when the engine is turned over, with the plug out, does not mean that the engine was not flooded. The lower part of the engine could still have quite a bit of fuel in it even after doing that test.
When the starter will not turn the engine over, have you tried removing the plug igniter and turning the prop over by hand? If it is pretty hard to do that, stop doing it because the engine is flooded and you need to get the fuel out of it first. Part of my start sequence is to verify the plug igniter is off, grab a prop blade and turn the engine by hand to ensure the cylinder is clear and the spinner will not be spinning a locked up engine. Out of long habit , I'll probably then flip it a couple of times as we did in the Era of No Starters and Castor Is King.
If you cannot pull the engine through easily, then lift the plane, roll it so that the engine exhaust port is pointed down, and rotate the prop until it gets easy to turn. Then raise the nose so that it is vertical, and you should probably see fuel drain out of the muffler.
The experiments where you were able to start the engine in the van and at home MIGHT simply be because you moved the plane around and happened to drain the fuel from a flooded engine.

All the above is not relevant if you have a two line fuel tank and you pull the engine line to fill.