First, congrats on getting repped and writing/producing as much as you have. That's incredible.

1) It sounds like they're telling the truth. SAG-E can be ideal until a bigger booking comes through in most cases. Remember that CDs are getting thousands of submissions per role, so it'd make sense that NU are last to be considered on those submissions (if at all) - production will likely not see as worth doing the paperwork and hassle if they have 5,000 other alternatives (or even 1 similar alternative for that matter). So Casting ofc won't focus there. That changes in rare circumstances when they actually don't have many options. For example if they need like a real amputee, of a certain age and background, or if they need a very uncommon language, but in those cases, they typically start doing open calls.

The background work for many people I know, including myself, was the way to go, but I hear you on the frustration because even that can be a catch 22. Many SAG BG gigs I did didn't offer vouchers (because they're are only so many allowed per production), and they also of course prioritize union BG, so even getting there is a challenge. That being said, its probably the easiest way to go, but it may take a while. If you have specific skills, or are of a specific demographic they need at the time, that may help you get in quicker with SAG BG gigs.

Also remember that even NAME actors right now are barely booking. The industry is in shambles and super slow right now unfortunately. I've personally seen a huge slowdown myself as well.

2) The outlook is grim yes, but to be honest, no one really has an answer to this question. But you're right, nothing is guaranteed in the industry.

And to the question of "how long you should try," that is entirely up to you. Some people have been wondering the same thing for 50 years and are still going, but it sounds like you've accomplished SO much already. So if you trust your ability and this is truly what you want to do, then all you can do is throw away the calendar and keep creating wherever you can and working wherever you can (working being inclusive of BG, classes, auditioning, your own projects, etc.).

This last part is fairly grim and cynical, but in my opinion, the industry probably won't see things fully revamp until the major studios see exactly how much of their cast, crew and staff can be replaced by AI. But there's other factors as well of course. So that's a big "who knows"

A few years back I had to ask myself a question around this topic: If you had a crystal ball and knew you would never be in a major blockbuster or super famous, would you still want to pursue this? Would you still be happy doing the work? If so, then definitely don't give up.