I am not sure if #2 is an issue for DW. After 4 shots, the SW is supposed to learn and update the table. However, if #3 is not resolved, we would have no way to verify if the table has been updated or not.
As for the slug probs, take a look at the DS website. They list two 28” barrel kits, one for pellets and one for slugs. Since the kits come with a prob, I assume the difference is the prob.
PS
For larger calibers, I’ve heard DS has been experimenting with Submoa barrels (take it with a grain of salt, I just heard it in a shop in the UK). If that is the case, I hope they are also looking at updating the probe.