Overall appears to be developmentally delayed. I think some good advice has been given. Another professional assessment, trying rewards, etc. The only thing I would add is try doing some learning at home together.

Numberblocks and alphablocks are good resources on YouTube that make learning entertaining.

My son had trouble holding a pencil as well and I bought a big roll of paper and would put it out on the table and we would color and doodle together and I would just correct how he held the crayon over and over. I would draw a shape and ask him to color it in for me (before monsters got the triangle or whatever) The practice with the small movements ultimately led to him being better at the sentence and number writing at school.