I have what I think is a conventional heating system (perhaps, maybe)
and have had several challenges over the years, must to do with the
motorised flow-control valve breaking.

More recently I have a concern with the pump. It's installed
vertically pushing against gravrity up to the valve where it splits to
the heating and the storage tank. On setting 1 it runs very quietly
but the pressure seems to be very low and the radiators don't really
heat up as they should. The water in the storage tank also takes
forever to re-heat. I am pretty sure there are no airlocks anywhere.

So, logically, I tried to set the pump speed to 2. The pump speed
picks up and makes a lot more noise and then stops and restarts
itself. There also seems to be a lot more noise in the pipes, water
sounds. But the end result of all this is a lot of air that I have to
keep\bleeding out every 15 minutes.

So, is the pump faulty?

Should it be installed vertically pushing against gravity?

There is only a 4" run of pipiong between the pump and the valve.
Could this be a problem?

thanks for any assistance/advice anyone can offer