Welcome to the world of being a poop obsessed bunny parent! I think there are a lot of us here haha.

I think giving a little watery critical care when you notice something is just slightly off is perfectly fine and a great thing to do (I do the exact same thing with my bunnies). The only time I wouldn’t is if you really suspect a severe blockage or bloat (like you notice a large chunk of foreign material was eaten, or something like that).

To answer your question about stress, it kind of depends on the bunny, but probably not too much. I think that they can pick up on our stress, but the type of stress causing small poops is usually something much more stressful (like perhaps a trip to the vet or maybe a loud dog barking outside for a long time).

Have you had his teeth examined? Lops are somewhat prone to dental issues, so that could be influencing his hay-eating (and poop size).

They can definitely be sensitive to certain pellet ingredients, so that sounds like a good plan as well. You might talk to your vet about doing a hay only diet for a little while to try to identify the problem (but important to rule out dental issues before trying that, to make sure they do eat enough hay).

Not likely, bunnies do pick up our moods, but not as extremely as that.

My rainbow bunny Breintje noticed it when I was in a lot of pain, and he groomed me a lot on those days. Sometimes when it was really bad he’d skip his afternoon sleep to watch over me in bed. It never affected his health though.

I’d say: rule out medical reasons first as well.

Of course it never hurts to work on bunny relaxation techniques. Some things that worked really well for Breintje were: letting him lay against my bare arm for skin contact, gentle rabbit massage, and purring together to create a happy and relaxed vibe. I wrote a topic about that last one:

Bonding with your rabbit: purring together to create a happy, relaxed vibe