In other words, you aren't going to get anywhere focusing on what you think it may be, what it is showing you or anything it says.  In contrast, here at the Illuminaughty we are happy to take everything you say at face value because this is the internet and we don't have time to run down your address and polygraph you.  Were you a demon we'd probably stick pins in your sigil and . . .well . . . nevermind that.

Okay, so you evoked something icky and now you can't get rid of it.  The reason the sage and salt water aren't helping you is because those are prevention tactics used to keep spirits away from your home.  Just like deadbolts won't keep out bad guys if you open the door up and invite the bad guys in, sage and saltwater aren't going to rid you of anything that is there by your express invitation.

The dream stuff is your brain assigning evil symbols to what you perceive as a negative/evil entity.  The little red demon face is a classic icon.  The used car salesmen is an even more insidious form of evil.  Believe me, I've got the vehicles to prove it.  But in the context of the dream the used car salesman is symbolic of someone giving you a sales pitch for something crappy.  Guess what?  That is what demons DO - they get all persuasive about trying to sell you on ideas that you are going to get one helluva deal one way or another.

Don't sweat the dream stuff.  Dreaming is a way your subconscious sorts out information you haven't sorted out in your conscious.  It just does it with symbols.  It's healthy, even when it is scary.

As for your pal the necromancer, it's a pretty good bet she doesn't know what she is talking about.  Getting rid of a demon is exorcism or banishment.  You don't need a spell for that.  And you surely don't need to try to trap a demon in a mirror.  Even if you were able to do that you wouldn't know how to manipulate the demon into being any use to you at all and you'd have reinforced the invitation to the demon.  Tell that girl to take two grimoires and call me in ten years.

The real problem is that you've evoked something and you want it gone.  But do you really?  When someone tells me they think they have opened a gateway to the dark side what they are really telling me is that they think they somehow stumbled upon a power inside themselves to achieve really big things.  I mean think about it - opening a gateway to hell would be a pretty BIG thing.  It would make you pretty special, no?  Well that's the sales pitch you've been given.

The truth is any yeehaw can evoke a demon if they go for it.  Controlling a demon, getting RID of a demon - those are more difficult skills - but getting one to show up isn't that hard.

So let's get you rid of this thing already.  You conjured it up, you can conjure it down.  But you have to really want to get rid of it.  If you don't, it will have a nice hallpass into your house until you tell it to get out and you mean it.

The entity is in your presence because you invited it.  Thus the authority for the entity to be there is YOUR authority.  However, your view on spiritual authority may not involve you being the highest power.  I don't know your religion, Adam, but I'd guess you were raised Christian based upon your symbolism.  You need to decide what you consider to be the ultimate highest power - your version of god, the supreme hiccup or whatever it is you think has the final say on all matters spiritual.  Whatever you believe - that is the authority you are going to use.  It won't do you any good to call upon something you'd like to believe, so don't go nuts calling on Thor if you aren't a Norseman.

Now you are going to design a little exorcism.  If you remember the name you used to evoke the entity with the Ouija board use that name to address it.  If you didn't use a name then you can wing it without the name.  Design a basic purification pre-ritual step wherein you do a bit of meditation, clean up and get yourself prepared to handle this thing.  Then mark out the entrances to your home.  Put together a basic speech that you can say with certain authority.  Since this was a freestyle evocation you can go with something simple, but structured.

"By the power of (insert your big cheese) I hereby command and expel (insert demon's name) from my home and my presence."

Are all demons this easy to deal with?  Heck no.  Here are some ways you can completely screw this up: