Hi chimphead,
Not sure why no one else has come on your thread to help yet, I'll do my best but am only a parent.
Firstly, by the end of year 1 it is hoped that children will have reached level 1b/1a of the National Curriculum (NC).
In case you do not already know how levels work, the first level of the NC is 1. Each level is split further but the letters c, b and a. 'c' is the lowest level of attainment, then b and finally a. So at this point in time a 1c would be a bit below where he's expected, a 1b is ok, and a 1a then no concerns. You can ask your son's teacher what level he has achieved so far.
Levels are being abolished from this September, however I still think this information will help you, because there are concrete examples for you to compare with your DS's writing:
This is a link to examples of writing judged to be at 1c
This is a link to examples of writing judged to be at 1b
This is a link to examples of writing judged to be at 1a
Now if you have concerns about writing and fine motor skills then please read the following thread, where mrz provides a long list of activities that will help children improve their fine motor skills, which will ultimately improve their hand writing.
I suggest that you work on a few of these exercises using materials you already have to hand and gradually find the ones that your DS is most happy to do each and every day.
At the same time try and encourage him to make up and dictate stories, letters, lists etc., whilst he is building up the strength in his hands and fingers with the exercises. This is to try and help him see that even if it is something he finds difficult now, there is value to getting things from his imagination onto paper.
This will also ensure that he works on many aspects of composing writing, without the current stress he is experiencing. If he is not confident with punctuation, explain it to him as you write his story/list or letter. Gradually you can encourage him to write the first line of the story, the first few words of a list, add the punctuation. You may well find that he enjoys writing much more as a team, at least for the time being. Little and often is the key.
Your other path is to see if you can get him referred to an occupational therapist, who can assess both his gross and fine motor skills. The ability to do this will depend on your area and I'm not able to advise you more than this unfortunately.
Finally have the school given him pencil grips to try? There are many available, although he is likely to prefer one or two of the various shapes. These can be particularly beneficial with ensuring he has the correct tripod grip when holding a pencil.