mostly they believe baby baptism saves, that good works earn you a place in heaven, that penance is necessary for salvation, that Mary is to be prayed to, and so on. Surely you don't deny all of this?
Infant baptism - yes, although in itself it won't save if the person later decides to reject God. I think you will find that there are plenty of examples from the Bible to both support and oppose infant baptism. If I were a sola scriptura Christian, I would have a major problem trying to reconcile an opposition to infant baptism with some Bible texts which clearly encourage it. But I might suggest that the sola scriptura position (on which I freely admit I am not an expert) seems to have a fixed idea on such issues and then argue from the Bible verses which agree with that and discount the ones which don't. Personally I don't believe that good theology comes from picking individual verses instead of looking at the big picture in Scripture.
'Good works earn you a place in heaven' - No, this is not Catholic teaching. Catholics teach that the grace of forgiveness and justification comes from God alone and can never be merited. Where we differ from some other churches is that we then believe that, after receiving the free gift of justification, our good works, which are in themselves the work of God in us, can help us to merit an increase in holiness. This is always a conditional merit based on co-operation with the saving work of Jesus, who alone has the power to save. Catholics do not teach that you can 'earn' heaven.
'Penance is necessary for salvation' - only if someone has definitively, absolutely rejected the grace of their baptism and decided against God (called mortal sin). Then, yes, a remedy is needed to restore them to God since baptism cannot be repeated. In other cases it is helpful in living a Christian life, not 'necessary for salvation' as such, which is not a term most Catholics would use on a day to day basis anyway since the tendency is more to concentrate on living life to the fullest to make the most of the grace Christ offers us to unite ourselves to him now and grow gradually more conformed to him in love rather than to scrape by on the bare minimum of what is 'necessary'.
'Mary is to be prayed to' - Not prayed to but prayed through in the same way that we ask our friends to pray for us. We ask Mary and the saints to intercede for us with God, not to somehow answer our prayers by their own power, which clearly they could not do.
I'm not expecting you (or anyone else) to accept the Catholic teaching on these issues. Just out of the Week of Prayer for Christian Unity 
, I am happy to think that there are fellow Christian sisters (and possibly brothers) around me who desire to be united with the blessed Trinity in love and disagree with me about some of the details of how this is worked out. What I think you should reconsider is the idea that there is only one potential understanding of all of these issues, and more, in order to be considered Christian. I would think, given the history of the Church, any Christian should be wary of a claim to an absolute and definitive understanding of an infinite and mysterious Truth.