Here is a good link for information on the pentagram, including the inverted one: http://www.angelfire.com/id/robpurvis/pentagram.html
Personally, I think you need to spend a bit of time researching into your projected path.
No, not all theistic Satanists worship demons, or even Satan. Satan is an angel by the by, not a demon, and his name literally means "The Adversary". Satan is the title of an angel more so than it is even a name, because within the Bible (and the unincluded canons) and the Koran it is used to describe several angels that God sent out to do his bidding. Yes, God actually told a Satan what to do, and usually when he had to, it was because humanity was being naughty again (which we did a lot in the Old Testament). I won't claim I've read the whole Bible, the Koran, or all the canons, but I've read enough to figure out that Satan is no devil and if he is, God probably made him to be that way.
However, I'll get back to my point about theistic Satanists. There is the Temple of Set for one. They are an organized group headed by a leader, and their main focus for worship is Set, the Kemetic god everybody loves to hate (except Kemetics it seems). Set was demonized over time in ancient Kemet (Egypt) due to his association with foreigners, with Ba'al, his murder of Wesir (Osiris), and his prevention of Heru (Horus) to the throne. They take this demonized netjer and basically work with him and worship him on his own playing field. I don't quite support them in everything, but I think they are interesting.
Temple of Set: https://xeper.org//
There are also theistic Satanists who worship Enki, a god who tends to do "wicked" things like Set does. I'm not sure on how accurate what I linked is, but it is the first information I ran into when I first looked into Enki and Enlil out of curiosity, and it lead me to some interesting information later on.
Enki and Enlil: http://www.halexandria.org/dward184.htm
There are other forms of theistic Satanist, I'm 100% sure, but I would consider the Christian kind the most prevalent, at least on this website. I would do some research into the other paths however, because they can be interesting to say the least.