1. Weber Q series gets great reviews. I also like Charbroil Grill2Go. Both are well made and have high lids so you can close the lid over your food.
2. I use OTA antenna but use the advanced forum search and it is often discussed.
3. To measure height it's easiest to use a broom handle held level with the top of whatever you are wanting to measure and held out to the edge of the RV and have someone else use the tape measure from that to the ground.
4. There are pin locks for the hitch pin. There are also some battery alarm systems sold (mostly motion sensors so might not work well with pets), but I don't recommend an trigger happy alarm as you are usually close to neighbors who will be pretty annoyed with you if your alarm is going off and you aren't there. Maybe one with a magnetic sensor for the front door would be better but I don't really see these either. Most just lock up when we leave, and some don't even do that. More likely to be broken into in storage than while camping.