Water changes must be done in large amounts if you are to be successful at breeding angelfish. Angels seem to thrive with 40% or greater water changes done as frequently as possible, even daily. You will probably not have much success with breeding angelfish if you can't change at least 30% once a week.
I think that WC frequency comes down to amount of bio load. I’ve never bred angels, but unless I’m missing something, it sounds like you’re saying angels need pristine water parameters to breed, meaning
>20 ppm nitrates or maybe even >10 ppm
I have one tank where I do 50% weekly to achieve that and another 50% bi-weekly to get the same results. My point is if his parameters are good, there’s no need to increase is WC schedule, if they’re not, then by all means, increase it.