What I mean by Dream Agent is: 1. they represent my genre; 2. they sell well in my genre. Sure, you can't know what their vision is for your book until you talk to them. But if you 'click' with a Maybe Agent who doesn't have the right connections, your book may stay unpublished. Or get published by a small imprint who has no resources to help with publicity. I feel that in that case, it's better to self-publish.
Btw, how long does an agent have to sell your book? If they can't sell it in X months, are you free to seek another agent and/or self-publish? I assume such things are in the contract?
First, why would you even be querying agents that don't represent your genre or have connections in it? They all tend to be very clear on what they do represent, and are not likely to list things they don't know how to sell, so your criteria seem more like a list for possible agents, not dream agents.
Second, this varies for people, but lots of agents take on clients for their careers, not a specific book. You want to find someone that wants to be with you for the long haul, and you want to be with them too.
Here's a hard truth, sometimes novels don't sell. And it's not a factor of an agent not trying. Even if you left them and found another, chances are it still wouldn't sell. There are only so many places to submit, and if an editor says no to Agent A, then Agent B is not going to send the same manuscript back just to be told no again.
If you end up with an agent, the book doesn't sell, and you end up wanting to self-publish, talk to your agent about it. Maybe they can help.
Again, this is all general information, and I am sure that exceptions exist, and contracts vary.