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I realize you are pretty far into this, and the YoLink is probably a better long term solution for you, but I'll share what I just found just in case it might work for you or someone else.
After a bit more searching this morning, I started finding incubation controllers of various types and came across these devices Temperature Controller With Relay 10A. Also these which have a little less control, but perhaps a relay that is more tolerant of Lithium battery voltages for the coil side.
What's attractive is that 1 device can control 1 heater pad, and they have the ability to set a low (turn on) point and a high (turn off) point based on temperature delta (basically hysteresis). Effectively solving the main challenge you're working around with the pulsing timers. Assuming you set the on temperature to be around 35F and the off around 50F, the built-in temperature sensor for the RV heater pad should be invisible. I like that the RV pad has a high temperature cutoff, which would function like a second fail-safe if the micro-controller didn't turn off their relay at 50F. The Lithium BMS will also shutdown at very high temperature as a third fail safe (belt, suspenders, and a parachute). As a bonus they consume very little power (less than most incubation controllers I found).
It does appear that these W1209 units in the first link above may come with a 14V max relay, and may fail sooner if used with Lithium to switch the coil side. The name says 10Amps, the product description says 20Amps, so I'll definitely check the relay specs when these arrive. I happen to have a 12V regulator output to power the Maxxair fan (because of a similar concern with over-voltage) so powering the coil side of the temperature controllers off of that should be compatible. It appears from the relay datasheet that you can use higher voltage on the relay side, it's just the coil side that has a 14V max. I bought 2 heater pads and 2 controllers. I plan to use 1 for a battery heater, and the other for a water tank heater, both units controlled by switches in the living space so they don't consume power during warmer days.
After a bit more searching this morning, I started finding incubation controllers of various types and came across these devices Temperature Controller With Relay 10A. Also these which have a little less control, but perhaps a relay that is more tolerant of Lithium battery voltages for the coil side.
What's attractive is that 1 device can control 1 heater pad, and they have the ability to set a low (turn on) point and a high (turn off) point based on temperature delta (basically hysteresis). Effectively solving the main challenge you're working around with the pulsing timers. Assuming you set the on temperature to be around 35F and the off around 50F, the built-in temperature sensor for the RV heater pad should be invisible. I like that the RV pad has a high temperature cutoff, which would function like a second fail-safe if the micro-controller didn't turn off their relay at 50F. The Lithium BMS will also shutdown at very high temperature as a third fail safe (belt, suspenders, and a parachute). As a bonus they consume very little power (less than most incubation controllers I found).
It does appear that these W1209 units in the first link above may come with a 14V max relay, and may fail sooner if used with Lithium to switch the coil side. The name says 10Amps, the product description says 20Amps, so I'll definitely check the relay specs when these arrive. I happen to have a 12V regulator output to power the Maxxair fan (because of a similar concern with over-voltage) so powering the coil side of the temperature controllers off of that should be compatible. It appears from the relay datasheet that you can use higher voltage on the relay side, it's just the coil side that has a 14V max. I bought 2 heater pads and 2 controllers. I plan to use 1 for a battery heater, and the other for a water tank heater, both units controlled by switches in the living space so they don't consume power during warmer days.
