Fred, with all due respect - and I mean it - 35 AH a day just for refrigerator and CO/propane detectors is way too much. In my trailer it's more like 12 AH a day, though my CO detector has its own AA battery. 35 AH would cover not only the parasiti loads mentioned above, but also lights, pumps and some TV or laptop time.
Now, about 1,500W inverter drawing 10A and 300W inverter only 4A with the same load - this means inverter losses 6A when the load is ~4A. I wonder whether I am the only one who finds this strange. Probably something was wrong with that 1,500W inverter.
About step-by-step photos or videos inverter wiring - OP asked. These RV mods are all DIY, members here would have some photos but with loads not exceeding 10A DC you don't need a guide.
DC input: Place 150-300W inverter within 6-7ft from the battery (extend its OEM cable #18 with a piece of #10 necessary), and connect it to the battery posts. With 20A inline fuse if you wish so.
AC output: I "think" that you can hard-wire inverter output to the closest 110V branch, ex. connect it in parallel to one of your 110V receptacles. Not to 110V 50A input outside, but exactly to wall receptacle inside. Electricians will frown on this, but you have mere 10A current. Make sure that 110V doesn't feed into converter - you might have to install a on-off switch on converter, or your converter might already have one. Don't forget to turn the inverter off when you are on shore power.
Yes, small MSW inverters are dirt cheap. Paid $20 for my 175W Gopower. LCD TV may or may not work on MSW, but 175W is enough for this load.