Running ethernet cable next to AC power cable in a conduit is a no-no for data corruption and power leakage concerns. It's between "Thou Really Should Not" and "Thou Shalt Never" with a very heavy leaning towards "Thou Shalt Never". It's not that the data will automatically get corrupted and you'll instantly fry your network gear and/or electrocute the next unsuspecting tech to touch the ethernet cable trying to figure out why your switch went up in smoke, but those are the possible concerns in the future.
Congrats on getting the 850' run working. Any tricks like using switches as repeaters in the middle? It'll work over the 100m rating in a simple run but after that point it's quite dependent on luck without special help. That would be the longest run of straight twisted pair cable I've heard of working.
Pretty much, you should never run low voltage, ethernet, etc, pretty much anything inside conduit with line voltage, as you'll get bleed over We don't even run low voltage thermostat wire inside the line voltage conduit to a/c units for that very reason.
My biggest concern in pulling that long of wire (except for it just not transmitting decently) was pulling too hard or kinking the wire, ESPECIALLY over the creek. That is why we jumped up out of the ground every 200' and put an LB, so we could pull only a couple of hundred feet at a time.
Funny story. .. we had monsoons, I mean HEAVY rain day after day, and that creek goes from a trickling brook to a raging river because it drains so much land uphill from us. In order to make sure the conduit was high enough, we had it strapped to a tree limb, but never had gone back and done any decent support to bridge the banks, so that section was simply about 40' of 1" schedule 40 pvc conduit, hanging in the air, resting on the far bank, which is higher than the house side.
Well, I and a employee had gone down to just watch the water run, when we spotted that line trying to float away. Sure enough, the wind had gotten up, the tree limb had broken, and now the conduit was stretched to the limit in a big swoop, bouncing on top the raging torrent of water, just WAITING for a big floating piece of debris to take it out!!! Both ends where it tied into the 1 1/2" conduit were bent over so far they pointed downstream too, ha ha. Talk about panic!! I just saw all of our phones, internet, etc getting ready to take off downstream!!!
With dual screeches of alarm, we both dove for the conduit and began to try to wrestle it back up out of the water and hoist as high above our heads as we could, willing the far end to release from the water. It seemed like it took forever for us to get the better of the fight, but finally the last few feet sprung loose and up out of the water, and there we stood, hands high above our heads, staring wild-eyed at each other, saying, "NOW WHAT????" hahahahha
Finally, we worked our way back to the errant tree and strapped that sucker tight against the trunk, as high as we could reach. Boy, talk about wear your butt out!!! To this day, I don't know why some large piece of debris didn't rip that line out and pull the whole board out of the network box, ha ha. Aaaahhh, good times!