Two of my kids are/were quite dysgraphic. I never went through the fingernail-pulling phase because I just accepted that this was very hard for them and that in due course they would either dig in and do enough work to remediate the problem or else find coping mechanisms. We did handwriting work only when they thought it was fun.
For my eldest daughter the handwriting work she did was probably 2 or 3 hours worth, total, prior to age 8.5. At that point she just started writing -- privately, copiously, messily at first, but gradually, after weeks and months of driven personal creative writing (not 'handwriting practice') she developed a fluid and legible script. For my son this meant he did 10 or 15 minutes every few weeks starting at age 9 -- almost nothing, really. He is 12 now and while he can sign his name and print neatly if he takes great time and care, he writes almost entirely on the computer, where he is a capable writer who enjoys what he can do.
If you are homeschooling you don't need to use written output to evaluate what your ds has mastered. You can observe, discuss and listen in order to find out what he knows. So written work has little of the urgent early necessity that it does in a classroom of 7-year-olds. It may be considered "normal" for a 7-year-old to write fluidly and legibly, but it is certainly not necessary outside the classroom, IMO.
Miranda