Improving efficiency of absorption refrigerator (ammonia+hydrogen)
I've come here for basically the same reason, however I have some suggestions that I've done and I believe they have helped.
And my fridge is basically the same as your, just a bigger model, same manufacturer.
Firstly I should suggest messing with the process (heat etc) would not be a good idea as I would assume the manufacturer would have optimized the design years ago, and I have heard over heating the boiler can cause catastrophic and irrepairable damage .
My fridge has a freezer box (shoebox size, quite useless) within the fridge and a heat sink next to it for the fridge part. I took the door off the freezer and cut the base out of the box, that made a huge difference, infact with it set on high on a cool day of 20c or less items in the bottom of the fridge will freeze.
But as the camping car is used mostly in summer and it's hot that doesn't happen then.
If you need a freezer use the engel.
The fridge is mounted permanently into the camping car with a door on the outside to access the back of the fridge, it has vents top and bottom, on the inside of the bottom door vents I've installed 2 mini computer 12v power fans, they are very week but do set up a positive upward circulation of air over the absorber/condenser. As these use so little electricity they can be connected into your auxiliary battery without fear of draining it.
I think the added circulation helps on hot days.
And finally if you can't avoid parking it with the rear of the fridge on the sun exposed wall try a shade cloth over the area.
Hope that helps.