Reoccurring Bent Axles, any reasons or upgrades?
The reason for the bent axles is primarily due to your riding a bike with a freewheel. Freewheels (as opposed to a freehub) have a length of unsupported axle on the drive side of the bike that is vulnerable to bending. That is the primary reason why freehubs were invented. As the bike industry moved more and more gear sprockets (6, 7, 8) this meant a wider cog and longer unsupported length of axle. It is amazing how many cheap modern bikes (Schwinn sold out their name for use on low quality bikes long long ago) are still using freewheels which are an obsolete technology at this point. http://sheldonbrown.com/freewheels.html

Improperly adjusted or worn bearings are not considered a major factor in having a bent axle unless the bearings are very destroyed and the wheel is not working normally. Bent axles are due to load. So, you using a heavy trailer and being a larger than average rider, the axle is more likely to bend.

Get a strong well build wheel with a freehub. If you want an axle of CrMo then make sure you are getting it. There are OK inexpensive wheels for $40 so at $15 per axle replacement (excluding labour) it really makes more sense to not be replacing axles. Joytech is a cheap hub. Buy a good quality wheel that is worth >~$100 and you will save time and money in the long run.

I'm curious what you mean by "bearing was catching...just burn it up" That sounds like you may not be adjusting things properly. Maybe review some insructions on doing a hub overhaul or go down to your local recycle a bike shop for some hands on learning?

I'm also curious how you could tell specifically by the mile when your axle bent? Normally a bent axle is hard to notice unless the wheel is removed.

I find that rear wheel axles even of freehubs can be hard to keep straight. My old parallax hub with an 8spd freehub would always have a slight bend when I took it off to examine it and this resulted in uneven bearing wear. Probably due to me carrying very heavy trailer loads, passengers etc. North American bikes are often designed for sport rather than long term utility so even a tall person may be outside of the design for the bike. My solution was to get an old new XTR titanium axle that was laying around in a parts bin at a shop I did business with. Since then my rear wheel hub has stayed well adjusted :-)