Are you referring specifically to the belief in Purgatory when you ask, “Does that mean one can have full faith in Jesus Christ, be Baptised, and Have repented and still not be saved if they commited too much sin?” If so, I think you’re misunderstanding what Purgatory is all about. Going to Purgatory is not the same thing as not being saved. People who wind up in Purgatory are eventually going to Heaven. Purgatory is a place of purification, not condemnation like Hell. Purgatory is to remove the effects of sin on our souls. Here’s an example that I heard once which I think explains it pretty well:
Say you and I are playing baseball my backyard and to prove my batting prowess, I boast that I can hit the ball into my neighbour’s window. To prove my point, I hit the ball through my next door neighbour’s window (sin). The moment the window shatters, I realise that I have done wrong, feel horrible about it, and immediately go to my neighbour to apologise and beg her forgiveness (repentence and confession). Being a kind and understanding woman, my neighbour accepts my apology and forgives my misdeed (or sin, if you will – absolution); however, she isn’t finished talking to me. There’s still the problem of her window. Even though I have apologised and been forgiven, it is still shattered. She continues on to say that although she does forgive me, she would like for me to pay to have it repaired (penance). I give her some money to cover the cost and we part ways. Two days later, she telephones me to say that she’s just received an estimate from a glass repair shop and the cost to repair it is more than the amount I gave her on the day that I broke the window and she needs a little more money. Having just spent my last dime, I tell her that I am now broke and have no more money to give her (death) but perhaps I could come work off the rest of my debt by weeding her garden, raking leaves, or doing other odd jobs she needs done (suffering in purgatory). She agrees to this; however, as I am saying this, my mother overhears me talking on the phone and knowing the situation – my misdeed and that I have spent my last dime – she offers to pay the remaining money to our neighbour on my behalf (prayers for the dead). After my mother sends our neighbour a check for the remainder of the money, I am finally and completely in the clear (attaining purification) and am able to move forward with my life (eternity in heaven).
I hope this helps a little bit!