Forget the chemicals.
First thing to do is lift the manhole covers, to check if it's a serious blockage, by either finding a full manhole, or where the toilet is feeding into the system.
Flush the toilet, if you get a good flush, it's further downstream, if it's weak, there's a blockage in the branch feeding into the manhole.
The branch is angled in the direction of the flow, so if you can find another manhole, and it isn't blocked, that's where the problem is.
Stick a brick in the clear pipe, then rod towards it....... get the wife a pair of marigolds to fish out the wet wipes etc that caused the blockage.