Here is what yur scenario is.
Your Tube Head running from the send output on Tube Head to input on Fender Solid state Return will essentially result in your Tube Head being the preamp into the solid State Power amp of the Fender. This will work ok(I do this using Tube Heads and it works great. I am not sure if there could be any damage result in a Tube head to solid state configuration. It might be hard on the Fender Transformer.)But even if this works ok, am not sure you will get the sound result you are after. As, people who use Tube amps
like myself actually prefer the sound of a TUBE Power amp. In your set-up you will be bypassing your Tube head power amp. A simple solution might be to get a nice Tube Preamp pedal like TONEBONE or something to give you a Tube Preamp sound into your Fender amp.
In addition, 2 (10's) on the Princeton is going to give you a nice tight sound, but not the low end you desire. You are best to buy a Head and cabinet at some point if you are after that type of "big" sound.
Just my opinion as others here may feel differently.