DJMC35:
I notice you're in Indiana. Somewhat north of me and I honestly don't know exactly 'how cold' it gets in your area.
With that in mind, I offer the following:
I think diesel gelation is likely an extreme low probability event in your area. There are plenty of other problems that occur that are seemingly attributed to fuel gelling when there may be a different root cause.
Sure, it can happen, I just think not very likely.
Try before winter making certain your fuel filter bowl is clean and fresh filter. If water is trapped in the bowl or filter element a freeze-up can cause problems.
You also mention adding a fuel supplement to only two- to five-gallons at the time. Are you keeping your tank full all winter? A full tank prevents atmospheric moisture from condensing inside the tank and perhaps freezing.
In my area we'll get to zero-degrees F for a few days stretch every year. Some years two or three times a season.
I've not used a specified antigel treatment added to fuel for the same reason you state: large containers, used sparingly; and additionally, even with our temps, a special-order item, especially in smaller quantities. And, I've never thought it absolutely necessary.
In hard winter I keep my tanks full and use a mixture of (1) Stanadyne (2) SeaFoam (3) Sta-Bil each added to the tank at twice the recommended dose. Others on this Forum over time have responded that this approach is overkill. Perhaps so. Cheap insurance however. I tend to use Stanadyne year round and a slug of Sta-Bil if I can't use my bulk tank--fuel stored under pressure--completely in about 45-60-days.
Never had a gellation problem, never had a freeze-up. Combined with a lower-radiator hose heater and a battery tender, our machines have always started when needed.
I'm curious how you decide to proceed and if you find a ready source for small quantities of anti-gel material as others here have reported the same problem of availability. Please post back your experiences so we may all learn.