Is there a respectful way to address a Catholic priest other than "Father"?
Military clergy, both Catholic or otherwise (Protestant or Jewish) are often called Padre. In Portuguese, priests are called “padre”, which is not the same word for a father, “pai”. As a matter of fact, the Portuguese word “padre” is only used for priests, having no other use. Granted, in archaic Portuguese it was used for father too.
The term Dom, is used for bishops and religious priest of the Benedictine Order.
I know a few religious (Religious Order) priests who are called Brother.
Some priests are called Monsignor, if they have been accorded that title.
Italian priests are called Don.
If you are really uneasy about it, I would imagine that the simple term of Reverend, would be appropriate. Do not think any priest would object to this phrase being employed.
Pope John Paul II as a young priest, asked his young friends to call him ”wujek”, which is Polish for uncle. In this way, the Communists would not know a priest was in the mist of the group and could freely administer the sacraments!
There are also Lutherans who call their pastors "priests" and "fathers." This is especially true in European countries.
Still have to chuckle a little about this as no one feels uneasy about calling the Founding Father of the United States anything else than the Founding Fathers!
Dads do not mind being called father by their children. And professors are still called teachers!