I realized there might be some issues with variable speed.
The mercedes has a few extra sensors to tell it when it is okay to switch to low speed. VSS and tps.
you only have temp.

I sugguest a bit of extra logic for the temp. Start the fan at high speed at the start temp. After a 4 degree drop, switch to med speed, another 2 degree drop go to low and shut off at the 10 degree total drop.
IF at any point temp increases, kick back to high speed. Not sure if you need to change the logic at this point to keep it at high, or if the switch up is enough.

I believe the 2 speeds I sent you plus high should be safe, I don't think you should put in any other inbetween speeds just because that would require more testing of the older fan to be sure it doesn't hurt it at other variable speeds.

I think this will need some drivablilty testing, in that does any of those speeds make it worse and if the up temp logic works.
I would prefer to verify this at warmer temps, but regardless it needs to be checked out.

Finally, if you have the time I would like to check out some stock mopar temp sensors to see if you can use those for temp. Now more than ever you need a temp sensor for this to work.