Hi Stalagmite,
Everyone's trip into these realms is unique, and yours is different than I've experienced or read about on this site. No cause for anxiety. Just enjoy the wonders of an expanding universe -- you have a front row seat!
The odds of finding a person who shares the same dream seem rather rare! Did you and Jeremy start a friendship or keep some contact information ? Perhaps the meaning of meeting him will become more evident later. I've had situations develop years after they were introduced 'psychically.'
It may not be necessary to 'know' that this fellow in the mansion is a lost spirit. 'Knowing,' the way it's usually said, means having physical proof, and he exists in the non-physical
If you treat him as a spirit and he does go away with the Helper, then he was a spirit and you have helped him move onward. At the least it's a step in the direction that has been offered you.
The Helpers have set up this situation for you, so they will be there when you're ready. In such a retrieval you are an actor (and a director,) acting out a role to keep this fellow from his preoccupation. The Helpers will take on whatever role you set up by introducing them to him. They want to get him to move upward into higher realms ('focus levels.')
It's hard to briefly explain how all this works. Have you read the short explanations posted at the top/beginning of this site?
Regarding your other dream of a section of a city --because many city buildings there are white, it seems you are visiting the 'Afterlife--Focus Level 26--27,' where we go after we leave the physical. Some people can get up there without permanently leaving their bodies, and maybe you are doing that.
Perhaps the bar is a place where you will meet others who will come into your life when the time is right.
Perhaps the people at the bar are old friends from your spiritual family.
You all could be sending your consciousnesses out there to meet each other, even though on physical Earth you are temporarily separated, geographically.
When you find yourself there again you could ask someone there where they're living now, etc --just a friendly chat. Perhaps their answers will give you clues.
The Afterlife is like an extra dimension. It takes some getting used to. Lucid dreaming and these retrievals are each a way into the afterlife. Enjoy!
Betson