So I've been working on the first book in a neo-noir trilogy this year, and I think one of my side characters needs some fine-tuning.
QUICKIE BIO (I can get more into the details of the character/overall story later if need be):
Joseph Irons is an extremely talented Minneapolis med student in his early twenties. Both his parents were about nine kinds of loaded (where they got their money from is never explained; Joseph pointedly ignores the question, implying some shadiness, and other character's explanations range from "started slavery" to "invented cough syrup"), and when they died in his childhood he was left a sizable inheritance. A devout Christian, but pampered and pompous, he started a private pseudo-clinic for the homeless, intending to quickly cure them of their addictions (which he thought was the only reason they wound up homeless in the first place) and reintegrate them into polite society. When he realized his patients, their problems, and his society were more complicated than he thought, his faith started to change and mature. He has since started giving free, question-free care to anyone who needs it - not, he insists, out of charity, but out of penance. He's generally well liked in the city, but still has a prominent naive streak and some leftover self-importance that others frequently call him out for. His optimism can be a little grating at times, but he's experienced enough to back it up and helps my main character address/get over a lot of the less-realistic aspects of her own (much more cynical) opinions and fears.
He's not especially important plot-wise in this book (though he becomes very important in the next), but he's a good counterpoint to/channel for my protagonist to work out more of her internal struggles. I just worry that he's leaning on Gary Stu territory and think he could use some more development in general. However, while the plot isn't centered on faith and/or lack thereof, it's a prominent internal subplot for my main, so I'd like to have an example of a good person who's very influenced by their faith.
Basically, how do I make this character appealing, believable, and developmentally influential, and how do I avoid making him preachy, perfect, and insufferable?
Help a poor girl out?