You can use the 🚫 marker in the crop planting menu to stop them from replanting. It won’t make them remove the crop while it’s growing but once it’s done they will harvest it and not replant.
In previous versions having a water wheel layout that didn't match the width of the channel didn't work too well; I wonder whether the latest water physics improves that. Personally I would be tempted to reduce the channel to two wide all the way down including over the (currently) missing aqueduct. Your dam increased the hydration to the left forest except during droughts but it's where all of your log storage is. Once you have haulers you can put food storage around your district but there isn't a good way of housing your beavers near their workplaces. Another benefit of the hauling post is that you can set it to minimum workplace priority so that it will eat the population fluctuations. I believe the water pump depth setting was added in the previous update.
@10:10 Pause the game, place the dams and then assign priorities to each one. Highest priority to the ones at the far end of course. Then the beavers "shouldn't" get stranded and/or build the wrong dams first.
Another content creator I watch has problems with flooding if they set their floodgates much above 0.75 which sadly rather defeats the object. Hopefully it depends on the strength of the water source compared to the width of the channel, so it might still work here.