Holy smokes, lots of scary "advice" today!
You have a regular spring suspension, so ignore all of the talk about jacking on the frame, as only those with rubber torsion axles have to do that. And yes, jack under the U-bolts that hold the axle to the springs.
Two issues with a bottle jack. First, never put a block of wood on top of the jack, as the small head could split the wood and your camper could come crashing down. Second, if the camper is not attached to the TV, it could roll and fall off the jack.
Much better, and safer, to buy a small floor jack, and a 3-ton should be plenty heavy enough, as you only lift one axle at a time. Don't forget to "crack" the nuts loose before you jack it up. And when tightening the nuts, after you have them snugged up, lower the jack to put a bit of pressure on the tire to keep it from spinning, then finish torqueing them to spec.
Once you have done one wheel, you will be amazed at how simple and safe it is. Just use the right jack, and you will be safe.