http://www.premier1supplies.com has some great tutorials about electric fence and solar fence - their catalog is great especially. They talk about the right chargers for different kinds of animals and different kinds of fencing situations.
The Parmak 12 is a good charger and should do well for you. The main thing is to make sure it is facing south, with no shade, protected from animals, and then keep all the weeds off the fence. If you can do that, the charger will do well.
In very dry areas, you can have problems with the soil not being conductive back to the ground. That can be an issue for me, but should not be a problem for you in WI.
The money for a small dedicated digital fence reader is well spent. It seems like you barely use it, but honestly, when you need it, it can save a lot of time and frustration knowing that yes the fence is on, and it’s got plenty of zap, or here is where the zap gets weak.
There is nothing wrong with solar chargers as an idea per se, but the cheaper chargers skimp on many aspects that affect longevity and zap.
If it’s possible/likely to touch two wires at the same time, it can be advantageous to ground every other one. That is the maximum zap path. If your wires are further apart, you would make them all hot.