For the first aid kit dont forget Benadryl, it can help fight anaphlaxis for example someone who is allergic got stung by a bee and is swelling up. And steri strips!! Way better than the needle and thread for most serious cuts, they just stick on.
For water you need something to purify it with so either a pot for boiling or I keep a military canteen which has the metal cup built in, or halezone/iodine tablets (yuck). If you have to strike out on foot you wont want to pack all your water along and it will run out eventually.
As for diabetes keep sugary snacks and juice crystals. A sugar low is treated with sugar, a sugar high is treated wioth insulin but is normally less immediately threatening than a sugar low. My wife's diabetic as well..
And yes I also bring the 870 especiallty if I dont have a hunting rifle... good for scaring bears or scaring wolves away from your pet dog. Good for signaling too. I got a few boxes of 3" slugs that I never could hit a deer withlol. But I would never actually shoot AT an animal unless I had to, just warning shots.