Is it permissible to give money or feed the poor as a substitute for fasting a whole month that I vowed to fast if I succeed, knowing that I am able to fast Ramadan but do not wish to fast the month?

A conditional vow is disliked because it does not avert anything; rather, it extracts from the stingy. Fulfilling it becomes obligatory upon the occurrence of the condition it was tied to. If you are able to fast, then fast to fulfill your vow. If you are unable but hope for your impediment to cease, then postpone the fasting until your impediment is removed. Otherwise, you must offer an expiation for an oath (kaffarat yamin): feeding ten poor people, or clothing them, or emancipating a slave. If you cannot find any of these, then fast for three days.