Tried the Blue Flame, will be looking at another way to heat

I found an interesting LPG fueled heater called Propex and is made in the UK.

It uses outside combustion air and vents the exhaust outside just like your original equipment furnace.

However, compared to your 80% efficient furnace it claims to be 93% efficient. The fan uses less than 2 amps compared to your RV furnace which uses 7 amps and up.

Propex heater;
http://www.propexheatsource.co.uk/heaters/hs2800#efficiency

One of about 6 USA distributors;
http://westyventures.com/propex.html