Connecting REALLY long(80‌‌~100 feet) input wires to arduino

I was originally hoping to connect the high level (top reserve) switch grounds together, which makes 3 wires on one tank. So 6 wires down the pipes.

In my opinion, this is how I would wire them.

Does using different ground wires for each individual switch give any advantage? Given the fact that all of those are going to be connected to a common ground/-?

Because they share a common ground at the tanks, there is absolutely no electrical reason to run a ground for each sensor.

Technically speaking, there is only 1 ground i this whole circuit, no matter how things are shuffled up.

The arduino is powered by the 12v wall wart, so there is 1 ground for the whole circuit...

One more thing, I recently came across an AtTiny 2313, which has enough input output pins for this purpose. I actually wanted to use attiny 85. but i need 6+2 pins for proper controlling. which the attiny 2313 has.

should i go for arduino nano or attiny 2313??
does load-shedding affect the ssr's negetively??
Can someone also help me with a model number for the TVS diode? apparently i cant find any here named zd1 online..

regardless, i have ordered all 3( nano, 85, 2313) of em, as i wish to play around.

I do realize that there may be ways of multiplexing to reduce the number of pins required. But i would like to avoid that, Unless, they provide any benefit over the latter..
(I dont have a programmer, so i use the nano as a programmer for the attinies)

This might be a silly question, But is it plausible to use a 12v liniear regulator lm7812 with the filter capacitors and heatsink as the surge protector?afaik, surges last for a very short time.
!! I will definetely go with the circuit suggested, this is just a noob-ish question i cant seem to find the answer for!!