I had a 2615HST. I used Power Service (the white bottle) fuel additive and installed a lower in line hose heater. Bought the KATZ lower hose heater at auto parts store. Drained radiator, cut 1" out of lower hose, installed in line heater and refilled with antifreeze. In winter I had the heater plugged into an appliance timer. The timer was set to come on about 2 hours before I got out of work. Heat rises so placing the heater in the lower hose lets the heated fluid rise and circulate ever so slowly through the engine and radiator. When I got home the water / antifreeze temp in the radiator was about 140 deg. which made for easy starts. This setup is much easier to install than knocking out a freeze plug and putting in a block heater. I still use Power Service in my new tractor but this one lives in an insulated and heated pole barn. I have 2 dogs that stay in the barn and a furnace that keeps it at 45 deg.
I'm surprised you have gelling using a kerosene / diesel mix. Usually the kero mix will eliminate the gelling problem. Are you using a 50/50 mix of diesel / kero.