A compenent fabricator/welder should be able to fix the frame issues easily.
Lippert has had its share of frame issues, but on an 8 year old RV how can you blame FR and Lippert? How many curbs did you jump? How many large pot holes have you driven over? See, if I was a warrenty person and you contacted me I could come up with lots of questionsmand reasons to deny any claims, especially age.
Not trying to be nasty, but really after 8 years and you expect some warrenty compensation? I understand your frustration, but after this long it really is up to you to get it fixed right, not the factory.