Was this an overly long kayak trip that what you were used to? Or just much more or strenuous paddling? Or had you been studying/writing more than usual before this?
If you have done a lot of rowing /training over the years you could have hyper developed upper body muscles, if you let those muscles relax and return to normal - you may get beyond the pain and compression issues.

The symptoms sound pretty familiar to VTOS.

[Can you have VTOS without blood clots?]
YES, you may never get a clot , but the risk of a clot will be there as well as the pain.

Expert PT and /or expert chiropractic may be able to help restore the body to where it used to be when there were no symptoms. But that does take time and a lot of care & focus on resolving the issues and healing.

I'd would wait and see what the venogram shows..then go from there.

But since there is not a clot to worry about right now PT may be suggested unless they find some anomaly that PT can't resolve. Make sure to ask for the best PT you can get.. and if that person does not fit for you find another one.

I would suggest looking into voice recognition or recording and other ways to study that will not aggravate your arm at all.

I would stop the rowing and find something much less arm intensive for awhile.
Take all the energy and focus it on healing for now.

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