Does your friend think this is always the right thing to do, or just when you happen to start out believing the right thing?

In theory, I think he'd actually say that this is always the right thing to do if you are pre-committed in various ways to a life based on X and which affects close relationships.

In practice, I think he'd welcome me with open arms if I was a Muslim/Jew/Scientologist/Mormon and told him I was having doubts and wanted to seriously consider Catholicism as the one true faith.

If God can't alter events that will affect our decisions, can he actually do anything in the real world?

Great point.

It appears that God is capable of everything, except when he's incapable of anything.

Another great point. I played praise and worship at a friend's wedding last summer as a non-believer (he asked and I wasn't going to say no), and one of the songs was this one(I linked to the chorus), which has this refrain:

Savior, he can move the mountains

My God is mighty to save, he is mighty to save...

Having that in my head for so long to practice it and what not, I came up with a re-write that illustrates your point:

Savior, he can move the mountains

But he can't do anything that's tangibly observable...