Is it permissible to address the maternal uncle who married the mother as "father" or similar, and is it obligatory to honor and be kind to him as one would to a parent, and do the rulings pertaining to a son and father apply to them? How should one deal with him if he wrongs you, and is one sinful if one does not honor or obey him?

It is permissible to address an paternal uncle as "father" due to his esteemed position and reverence, based on the Prophet's (peace be upon him) saying: "The paternal uncle is a father." However, obedience to him is not obligatory, and one does not sin by failing to be dutiful to him, but it is obligatory to maintain ties of kinship with him in a good manner. If your paternal uncle wrongs you, it is better to forgive and respond to ill-treatment with kindness, as Allah Almighty says: "And not equal are the good deed and the bad. Repel [evil] with that which is better." Nevertheless, it is permissible to respond to his injustice with an equivalent measure, without exceeding it.