Are freewheels really that prone and susceptible to bent axles?
It almost certainly won't happen with a cassette hub. It can happen on standard axle cassette hubs, but it takes a lot, and there's basically always a dropout alignment problem at work in addition to heavy loads over time when it does.
Eight and nine speed standard axle (M10 or 3/8&quot;) freewheel hubs are the definition of a cynical design. They work terribly and exist only because hubs are fairly reliably overlooked by buyers of entry-level bikes. They're an utterly crass means for product managers to jam more bullet point type features into a given price point. They are that bad. Light riders are spared some of the pain, but what you're dealing with is common for heavier riders who wind up with them.
Five and six speed standard axle freewheel hubs put much less leverage on the axle where it protrudes from the locknut, and have a pretty minor version of the problem, even for a somewhat heavy rider. Seven is kind of in the middle but is not that problematic for most.
You could put in a solid Wheels Mfg chromoly axle, which means switching to nuts instead of QR, and it will mitigate the issues a lot. It's unfortunate if you haven't had that presented to you as an option. I don't necessarily recommend it though, compared to just putting the money towards a new wheel and cassette.