I read the 95 Theses and i will say that he was a Christian.
The first 4 are readily found in scripture, and i agree.
1. Our Lord and Master Jesus Christ, in saying, “Repent ye, etc.,” intended that the whole life of his believers on earth should be a constant penance.
2. And the word “penance” neither can, nor may, be understood as referring to the Sacrament of Penance, that is, to confession and atonement as exercised under the priest’s ministry.
3. Nevertheless He does not think of inward penance only: rather is inward penance worthless unless it produces various outward mortifications of the flesh.
4. Therefore mortification continues as long as hatred of oneself continues, that is to say, true inward penance lasts until entrance into the Kingdom of Heaven.
This can all be found in Matthew 25: 31 to 45 James 2:18, Romans 7: 14 to 25
The rest of the Theses seems to me about the Pope remitting punishments, the only ones he can remit are the ones brought on by his order and has nothing to do with God, which i agree.
And indulgence,s which in these days any one who can read can see is not of God but of the devil.
But in those days many people could not read and very few had a Bible, they only had what the Church wanted them to have.
Shalom