The word "Pagan" means NON-CHRISTIAN.
More precisely it means non-Abrahamic religion, non-Christian, non-Jewish, non-Muslim. Some people will exclude also the other bigger world religions, Hinduism, Buddhism etc. as the term has a slightly pejorative sound. In the beginning the word was used of people who were seen as too primitive, uneducated, stupid to be Christian.
If you keep "Christ first", you are Christian, not a Pagan.
If you believe Jesus is just one of the Gods, you are not Christian, you are Pagan.
It's not a question of people telling you what you may or may not believe, or setting rules and limitations to spirituality. It's a question of the correct definition of words and the correct use of language. You cannot start defining the words for yourself and call you what ever you like simply because you like the sound of it.
Antisemite means a person who hates Jews, not a person who hates the Semitic people. Antisemite is a misnomer in that way, but it wasn't at the time, when one meant the Jews with the Semites, the time it was created - by an antisemite, in order to create a word that sounded more clean and clinical that "Jewhate".
Pagan is non-Christian. You cannot be non-Christian Christian. It doesn't matter if you like the sound of "Christo-Pagan", or would like to call yourself one. It's not yours to decide. The word has been around for 1600 years in the definition "non-Christian", so it's not just some conspiracy against you and your right to define yourself.
Of course your religion, faith, spirituality, life philosophy and all that is your private matter, and between you and your God - if you have any. Parents have some say in the spirituality of their underaged children, but adults may define their spirituality as they choose. Nevertheless, this is not a question of beliefs, this is a question of language, and you may not define the language to your liking.
Respecting your ancestral religions at the same time as accepting Jesus as your savior doesn't make you a Christo-Pagan. It makes you a respectful Christian.
To have been raised as Christian and later given up Christianity for Paganism doesn't make you Christo-Pagan. It makes you a Pagan with Christian upbringing. Christianity is not ethnicity, like Judaism. (Meaning, if you are born Jewish but later converted to Paganism, you can be Jewish Pagan, but being a Jewish Pagan doesn't mean you combine Judaism and Paganism as your religion. You cannot be religiously Jewish and Pagan at the same time. The words are antonymes.)
Having melted Christianity into Paganism or Paganism into Christianity and created a new religious system meaningsful to oneself doesn't make one into Christo-Pagan. You are either a Christian with Pagan style devotional system, or Pagan with some Christian inlays in your faith. You cannot be both at the same time.
You can incorporate to your Christianity the belief that Nature is part of the Divine - after all, there's some Biblical support to this idea - but you're still Christian, and not one bit Pagan. (Besides, not all Pagans believe that Nature is part of the Divine. There is really no other definition of Paganism but that it is not Christianity...)
You can be a Witch and a Christian at the same time - if by being a witch you mean a profession, lifestyle, hobby, not a religion. If by being a witch you mean a religion, more precisely Wicca or some other Neo-Pagan form of spirituality, then you can not be a Witch and a Christian at the same time. Wicca is a Neo-Pagan religion. Pagan - even with the Neo-prefix - still means "non-Christian". You can pick and choose features and elements from Wicca to incorporate into your Christianity, worship Jesus with Pagan rituals and ceremonies (after all, what is Christmas other than stolen Pagan ritual?), and take everything you like, except the belief in Goddess the Mother and Her Consort the God. You can even define One God as Goddess. You are still Christian.
Also, being a witch IS practicing magic. Of course, the majority of today's witches are very lazy and "forget" to practice magic, but if you think it's a sin to practice magic, forget your idiotic idea of that you'd be a witch. You really aren't a witch and you don't even want to be.
Pagans don't believe in Devil and are not Satanists. Satan as the Devil, the evil God, is a Christian invention and inherently bound to Christianity, which makes Satanism non-Paganism. Now, there are several opinions on whether the Satanists, who worship Satan (Shaitan) the Pagan God, are really Pagans or not, and that depends totally on whether there really ever was a God Satan - which, as far as I know, there never was, but I really don't care how the Satanists define themselves. It's none of my business. (Well, is this then? Yes, it is, because I'm a Pagan, and I will not suffer Christians trying to steal my religion from me as well as my feasts. You have made your bed, now lie in it.)
A girl I know claims to be a "Pagan-Christian Witch" - she believes being a Witch, Wiccan and Pagan are the same thing and that there's only one rule in being Christian - to believe in Jesus... You can basically ignore all of the Bible, even the 10 commandments, if you just believe in Jesus. I know there's a lot of Christians who have the same idea of what it is to be Christian. It really doesn't matter, because BEING PAGAN IS BEING NON-CHRISTIAN.
You cannot be black and white at the same time.
You cannot be a cat and a dog at the same time.
You cannot have the cake and eat it too.