I think testing would be a good idea just for clarity on what's up. You mentioned fine motor issues, for example. I'd want to know if the issues you're seeing are simply developmental or if they are due to a disability that will continue to impact your ds as he progresses through school and through life. If it's not something that's going to resolve on it's own through maturing, your ds will benefit from starting on accommodations (or remediation) *now* rather than later on. One note - you mentioned the "careless" mistakes on the math test. If it's a one time thing, it's probably nothing. Even if it's an all-time thing maybe it's nothing. But fwiw, making "careless" mistakes on math work is one of my dysgraphic ds' biggest challenges with schoolwork - his dysgraphia causes him to switch numbers around accidentally and make mistakes when copying from one line to the next in his work.
Testing might also show you that there are issues causing or related to the SPD behaviors - that happened with our dd11 who went through therapy for SPD at 4 (which helped some)... only to find out a few years later that the real issue was something very different.
Best wishes,
polarbear
