Welcome to the forum.
We have a Hemi 282 RK TT new-- about 33' tongue to bumper, and while we don't go "off roading", we have absolutely no complaints or qualms about the construction of the frame or superstructure. (Yes we did have a problem with the black tank slipping out of it's cradle and, from other posts, some have had the same problem with their grey or fresh tanks too. Make sure your dealer knows you are aware of these potential issues.)
Getting back to the frame issue, I agree with you, I find it unlikely the frame twisting just by putting it up on leveling blocks.
I agree, FR does not give the owner a wealth of knowledge, especially in the Salem line, you can't seem to find a good phone # anywhere and particularily on the Salem or FR web site. Perhaps ask your delaer who their contact person is. I did that and my delaer was very helpful.
I found 2 phone # contacts for Forest River Industries in Elkhart, IN:
I'm not sure who this will get you to but ask to speak with the Quality Assurance Director / Manager or the Sales Manager.
Hope this helps in your decision.
Mark, Vicki, & Scout THE dog
2015 Hemisphere 282RK
2010 F250 Super Duty
1992 Goldwing Aspencade