I don't think those tripods are capable of supporting 2500 - 3000 pounds of weight.
Here's a simpler solution. Put blocks, concrete or wooden, under the frame of the camper near the front. Then you can lower the camper onto those blocks. It's stable, well supported, and the trailer won't move on you. Be sure your tires are chocked real good too.
If you don't have any jack stands, like in my photos below, you can use wooden blocks, or something else. Just be sure whatever you use will not collapse:
If you need more height, add more blocks under the jacks and then raise the jacks as high as they'll go. Then insert the supporting blocks under the trailer frame:
