Hi Shalom:
Welcome to MS. You might want to take a look at:

If you want to do this exercise, write it to one person, rather than both. You might want to start with your father if that is easier for you. Write it as if you are not going to send it (and you don't have to send it.)

It's really created for the survivor's benefit and you can get a handle on what is difficult for you. Suggest you get a therapist who understands male victimization issues. You can find the link in "A Consumer's Guide to Therapist Shopping" if you don't have a good one.

Good luck and welcome to the community.
Blissfully retired after 35 years treating sexual abuse