That are big misconceptions, no rational miner is going to continue working on smaller chain, because longest chain = Bitcoin.
Again, you don't understand the consensus mechanism. Of course a rational miner will continue working on a smaller chain if the longer chain violates his consensus rules.
Even today there can be many forked ledgers (miners building on top of smaller chains), but there is little reason to do it thats why you dont see it today and wont see it in future when the hard limit is removed
Actually, the limit specifically prevents any disagreement over what constitutes a valid block in regards to size. Without that limit, the entire network must
trust all miners to never disagree on the size of blocks they are willing to validate and relay.
Bitcoin is built on the premise that actors will act rationally. Its functionality
should not depend on rational actors being
correct. Rational actors are wrong all the time; consider all the companies that are constantly going bankrupt. Doesn't mean they were irrational; it means they were wrong.