Congratulations on getting the clog out. Sounds like you are on the way to having the thing function as it should.

As for the inlet pipe leaking, I think if you can fit another O ring in there, you could try that. Sounds like the O ring (even though Ford) is not of the correct dimensions needed for your waterpump/tube application. The vaseline would take the place of a silicone grease and not to really stop leaks, just to lubricate the O ring so it doesn't bind going into place.

The vacuum line (tube) that you are referring to is just that. If you found one damaged either cut it back or replace it. It will be a reason for no heat, but not for the gauge not working. The heat sensor on the engine will make the gauge work.

Please keep us posted.