You sound like an amazing supporter. Your partner is lucky to have you in their life. I know I wouldn't have made it through PA school without my wife(and kiddo for that matter)- even though she was 3 hours away most of the time.
1.) Maybe a cheap but sturdy "carry-on" luggage set? Being able to roll ones clothes around from place to place might be really helpful if they don't have it yet.
2.) AirBnB gift card, but if you don't have a large budget this could get expensive fast.
3.) Christmas - if he has off - maybe just plan a night away somewhere where you both can relax and rest? Couples massage?
4.) Cheap ideas: Get him a "stethoscope pal" in anticipation of his pediatrics rotation. Putting a little bear or something on his work uniform / instruments can go a long way to ease those little minds n' bodies.
5.) Books:
https://www.amazon.com/Pocket-Medicine-Dr-Marc-Sabatine/dp/1975142373
https://www.amazon.com/notebook-Medical-Physical-templates-perforations/dp/B01HU696MY/
6.) A bunch of decent gel pens. These will be stolen from him or lost, but having an abundance is great to have.
Good luck! If you have made it this far, you probably have what it takes to see it through to the end.