Why would you be an FO for life? Even with all the retirements coming up at the majors? Is there an underlying reason why you wont ever upgrade? (Health, dui, failed checkrides etc.)
Also, when you say "heavy jet pay structure" do you mean similar to a major carriers pay? Is this corporate department airline A or B that you mentioned? Or is A and B two other airlines besides XJT? Not enough details my man.

Do you value the QOL increase at the new corporate job? I personally as a single male in my early 20's would prefer to fly more than 200 hours a year, but if the pay is right and it was my home town id consider it. However, corporate departments can come and go as fast as regionals. However, finding a corporate job will be easier once you are corporate. I have flown corporate and it really is a small world. I made a few connections in just a few weeks at other major corporate departments. That is what its all about in the corporate world.

As for ameriflight, tpic might help, but its single pilot on steam gauges. High end jets, and airlines may value multi crew sic time more. It depends. But thats what i understand of the airlines. Single pilot although a skill in its own right, is nothing like flying glass as a crew. I would not leave XJT for any cargo outfit that A. Isnt part 121, B isnt a jet/turbofan multi engine/ multi crew operation.

Honestly from you first sentance or two, It soundslike you have had a few bad days or weeks at XJT and just want something new. Speaking from expeirence in making quick decisions that in hindsight I should not have made because they were emotionally fueled. Id say give XJT a bit more time, keep your chin up and wait for at least said "Airline A or B" to call in a year or two, or get some decent TPIC at XJT. You have decent time but nothing that will scream out to corporate departments for a capt spot on a jet. and like all airline and corporate pilots. NETWORK!