More webasto issues lead to adopting other measures

I'm continually getting trouble with my Webasto 5500 which won't stay on. It shutdowns randomly with either a F1 (mostly) and F2 code. The diesel tank is full with fuel from auto diesel stations. The trouble now is that the worst of the winter is still to come and my boat isn't winterized as I want to use it and live on it part time during this time.

Heating the boat without a diesel heater.

This basically means electric heat. The 439 has all A/C sockets on a single 15A ring/breaker. The micro wave is on the same ring. This means if we have a heater turn on then we need to turn it off while using the microwave.
We own 2 West marine 1500W heaters. They draw 10.3A maximum which is a long way from 1500W but that's another story. I can run both these heaters on the 15A ring at setting 3/4. This draws just under 7A per heater and results in more heat than one heater on 4/4 which draws 10.3A.
The water heater appears to be on its own 15A circuit also. This is shared with the battery charger I think which is a 60A unit. This means 6A is pushing full power. The water heater is plugged with a euro style plug in to a socket behind the galley couch back (beside the water manifold). I ran a heavy cable from there using a Euro to US adapter and this lets me run this ceramic heater instead of the water heater.
So, now we're at a 10A west marine heater and a 13A ceramic space heater. It isn't enough to keep the boat comfortable.
I realized that I'm not using half my boats power. The boat has 2 x 30A shore power cables. One is for the boat and the other runs the 3 A/C units on the boat. I unplugged the A/C shower power cable. On my Jeanneau, the cable is a 50A 125V ending. I had to buy a 50A 125 to 30A 125 pigtail. Then I purchased a 30A to 3x 15A 110V socket which is protected. I can run another space heater from that.
This puts me at a 10A, a 13A and another 10A.

Dedicated 400W engine compartment heater.

I also added a 400W 110V AC Caframo engine heater. This is a heater which turns on at 41F and turns off at 59F automatically. I installed it temporalily in the front of the engine compartment with zip ties for now. This should prevent the engine from having problems from the cold.