Welcome to Connest @lanaeg.
His doctors have done what they can do and this recommendation is a worthwhile option. It is possible to request a video visit after sending results of all the testing to a referral institution like Mayo. His doctor can help you to get this done and recommend what specialty the referral should be made to. Travel and waiting for an appointment do not sound like a viable option given his condition. What is his age and are his symptoms progressive? I can only imagine how worried and frustrated you are at this point.
My husband's cancer was diagnosed at Mayo from the scans and lab results that were done at home locally. Things were missed there, and only because he had scheduled an executive physical at Mayo was he diagnosed and treatment started. More opinions, larger referral centers may lead to better results.