Honestly, I think I would signal and carefully merge in that second situation. You're technically merging into the traffic lane if the shoulder disappears and the lane jogs to the right, so I think the burden is on you to merge safely there rather than the driver. But to evaluate who was "in the wrong" probably depends on the specifics of the situation (who was in the traffic lane first, etc).
The first situation is just commonplace driver stupidity. You can head off a lot of that simply by moving into the middle of the lane a bit earlier.