Bypass hose

Where are you getting the hoses?
What brand?

Even if one end of the bypass hose was completely plugged I would not expect the hose to do that.

Have you checked you rad cap. It might be stuck closed causing excess pressure on the system.

IMHO the water pump would not be able to produce more pressure in the system than a 16 lb cap can. It is only there to circulate the water and while there is some resistance to movement through the engine I doubt it is a lot. (I could be totally wrong)