Where Tim is is the loess hills formation, basically blown in silica, mica, silt, and vegetation, right next to a major river and floodplain where the heaviest formations would be. Add in the fact it is on a severe grade I can't believe it stayed as nice as it has. Looking at the pics I say the fiberglass did its job...very few cracks other than the control joints. Concrete around here with mesh always seems to crack and show the mesh lines, the control joint down the middle might be a good thing, mine was poured in 1980, 12ft wide 144 ft long, with mesh, and it cracked right down the middle just like the contractor said it would after the first 20 below weather we had. So cut or not you would have a crack there, just my opinion but I think your contractor did a good job given the soil there, maybe some rebar would have helped, but I bet you would have even more cracks. When they built the interstate near you in the 70s they dug down to light brown dirt and pulled a the dark soil out and filled it in. Remember how the hills were dug out around you years ago, a lot of that was from the interstate construction to get better soil. If that $4500 bid includes digging the old caulk out, grinding the edges, new caulk, and a warranty jump on it. We both know no way it all lasts 8 years.