I have been going through a somewhat similar struggle, when to switch to technology and give up on the handwriting. My ds is 11, 5th grade, so it was easier for me to decide to make the switch. We are diagnosed dyslexic but suspecting dysgraphia, since lots of issues have not corrected themselves.
We also have been dealing with lots of self doubt, stress, and some anxiety this year. The workload got to be too much, slow reading and slow writing. He reached a point of just really shutting down, grades went down, and feeling aweful. The homework wars were starting at home since he really never wanted to get started on something he hated. I needed a break and so did he.
I set him up with an IPAD and keyboard and learningally account over the weekend. It is a night and day difference. He can actually feel like he can keep up with the pace without relying on me all the time to scribe or read for him. We will see how it goes, but how long do you work on handwriting before you just say enough?
I have the philosophy that we should remediate everything as much as possible, all the smaller skills. The younger they are the easier it is. I also have the philosophy that kids need to enjoy learning, feel successful at something, and not live a stressed out life.
If it were me, I would ask for an alternative. I would hate to poison the one time in the day where he feels so smart, successful, and not different.
I also wouldn't discount technology. It would be much easier to incorporate a great math app because he is successful without the OT there.
Only you can make the decision.