1) You are correct. It does happen, and you didn't even mention that it is not possible to place the properties dialog where you want in a multi-monitor configuration.
2) You cannot hide RT fields at all, neither within nor outside of tables, neither with or without a space. It will always only work, until someone adds his/her own hide-when-formulas inside the RT field. Consequentially, you shouldn't even consider this design technique. Now, call that a bug or an inconvenience or whatever, but that's the price you pay for the power RT fields give to the user. I believe, that this is what Ben has been referring to.
3) It seems you do know what to do to make the Principal field work (as laid out e.g. in the agent FAQ), but refuse to walk that rocky road. Point taken, but personally, I find it absolutely acceptable, that this issue is covered by Notes standard security. Plus, it is hardly a Domino Designer issue.