Are you full-time? What does your work involve outside of Sundays? Would you also be delegating music ministry on Saturdays?

If Sunday masses are your main responsibility, and you're missing ~12.5% of them (even though you continue the background organization/preparation), that is a lot imo and I think would exact some cost on your perceived reliability, if not get refused outright. This is a job with some specific sacrifices attached, namely of free weekends.

There's also the choir's sense of you as their leader to think about.

I'm part time with responsibilities on Sundays and major feasts, and take 2-3 Sundays off per year. But I don't have paid section leaders or a large choir, so it's palpable when I'm not there.

If you have weekday duties that you remain ~100% on, and the choir(s) still execute well when you're away, it might be fine. It does sound like you've created a well-oiled machine.

^^^^^^^

/a good pastor-employer is hard to find/

(Flannery O'Connor never got around to writing that short story)

I’ve been in the role for about a year . . . I’m paid hourly and have PTO available, but I’d even be willing to take unpaid time off if needed . . . In your experience, what’s a reasonable number of Sundays off per year for someone in a position like mine?

In my experience, the number of paid vacation days is typically regulated at the diocesan level, but the pastor can expand it unofficially/informally. Two weeks is pretty typical in the first two years of employment, but see what your diocesan personnel handbook says about holidays, holy days of obligation, and whether you're entitled to an additional day off when scheduled to work on a holiday/holy day.

And the frequency of weddings will taper off as you get older. You need to go to those weddings, and a good pastor will understand.

The first statement is true. I would say the second really depends on how close you are to the couple. Some college friendships endure long-term, others don't. If they're getting married out of state, how often will you see them in person from now on anyway? If you were the one getting married, would you realistically expect them to travel across the country to attend your wedding? If not, you shouldn't feel obligated to travel for theirs. Consider asking a parent, family member, or friend of the opposite sex who knows the couple in question, who may have a more objective perspective on whether the friendship is close enough to justify traveling for the wedding.

This is a job with some specific sacrifices attached, namely of free weekends.

Indeed it is. I worked many years without two consecutive days off most weeks, and three-day weekends were nonexistent without using PTO. I saw a recent job posting that included something like five weeks vacation and more (including Sundays) for professional development and out-of-town recitals (clearly they were wanting to hire a concert organist), but that is extraordinary for the first year of employment. I know a music director who's now able to take up to eleven paid Sundays off, not including sick leave, but that's also extraordinary.

In my experience, priests are typically entitled to about two months paid vacation, and most of them use all of it, even those newly ordained. That is something to keep in mind. Does your choir take a break at any point? In any case, it sounds like you have competent substitutes available with minimal to no disruption. Since nobody else has mentioned it, if you're being asked to do music for weddings elsewhere, you need to make sure the couple has cleared the use of outside musicians with the resident music director. Beyond professional courtesy, this may affect their fees, so always ask and never presume. One last tip: Don't tell your choir in advance when there will be a rehearsal substitute! You might be amazed how many otherwise reliable choristers will use your absence as an opportunity to play hooky.

weddings….are all weekend events. Beyond that, I also hope to travel a bit and take occasional breaks throughout the year for rest and perspective.

As others have said, I think your weddings may be your travel and breaks in this season of life.

I (FT and older than you) am glad to have four weeks of vacation each year. Legally, that’s 20 workdays off, so I could take 20 Saturday PM + Sunday AM off. But, as St. Paul said, “all things are lawful unto me, but not all things are expedient”.

I enjoy traveling on weekdays when the roads are calmer and the hotels and restaurants are cheaper. And I try to keep to 4 weekends away, as I trust my subs, but do believe I’m the right person for my job, and want to carry on the relationships I have as much as possible.