Your breakers
Mobile Homes are NOT cold as a rule. -There may be a problem with your furnace or baseboard heaters. Get a good handyman to check it over.
No, PVC is not rated for 180 degrees which is the average operating temperature for baseboard heat
None. Probably the home was built for forced air and converted to boiler/baseboard heating.
Answer No, if the current to the baseboard heaters is off they can't run or heat.
Baseboard heaters depends on convection currents in air to move heat around a room.
Not really. Baseboard heaters are rated in watts. W = Amps x Volts has not changed since electricity came into being. What has changed are some of the designs of the baseboard heaters. Some heat oil in the baseboard heaters, which dissipate the heat out at a more even heat. On the market now are new types of thrermostats that pulse the baseboard heaters for a more regulated heat rather just turning them on when the thermostat calls for heat and turns them off when the thermostat is satisfied.
depending on conditions but generally a heat pump will cost you less to run.
Yes they work well if the room is insulated well but if it is not sealed well then it doesn't heat as effectively and it takes quite some time to heat up a cold room.
Yes. You might want to check to see what recommended temperature is for water entering the baseboard units and insure the water heater will meet that. Something else to consider is that there will need to be a pump in the water circuit to circulate the water. A tank type water heater would also work to store hot water until needed by the baseboard units in an instance where heat might be generated at a time not needed by the baseboard units.
With adpaters and push nipples as supplied
About 150 deg.
First,I would check the houses infiltration rate and try to improve it. Second I would look at the fuel efficiency rating of the equipment and improve things there if it is an older unit. Vent placement in your case is trivial, returns belong down low where the cold air is.