It seems that ideally, we should feel solidarity with similarity of mind

Hm, this runs counter to my view of the future. I see the future as a radical differentiation of minds. From this perspective we should fall in love with difference/weirdness, etc.

Are chimpanzees and dolphins so intelligent that they shouldn't be experimented upon?

Yes :D

Should we feel less solidarity with a human that is less intelligent than a chimpanzee, than we do with the more intelligent ape?

I've never felt comfortable with this comparison. My mother works with mentally handicapped people and she once said something similar, essentially comparing the mentally challenged with the cognitive capacities of a chimpanzee. But this comparison does not make sense. A chimpanzee that is particularly intelligent doesn't become "more human" and a cognitively challenged human doesn't suddenly become "chimpanzee-like". We are completely different species with different genetic make-up, and with humans also inhabiting a symbolic order that is pretty much completely absent in the world of the chimpanzee.

Then there is solidarity of place: We decide it is better that many Iraqis die, rather than risk fewer American lives. In questions of climate change and economics, there is also solidarity with those in our time. Or mix them up: Someone doesn't buy leather goods, because they are made from animals, but buys cloth goods made by people in sweatshops.

Ya, these are great examples of flaws in modern logic.

We should be so lucky that in 2493 it is in our hands to make such judgements.

Agreed, it's hard for me to imagine biocultural humans (as we have known them) existing that far into the future.