Butcherblock island with waterfall edge

I have questions/second thoughts on what seemed a straightforward build. I don't want to rush small details that could tend to have consequences over time.

I'm building and island with a 1.5"x72" edge grain, laminate Acacia countertop with waterfall edges. I plan on sealing with mineral oil.

Here is a mix of what I read/learned and my further questioning.

Thanks to you if you take time to answer any point

1. It's common knowledge that wood needs to expand and breathe. That being said, edge grain laminate wood countertop should only expand on it's width.

Should I use expansion holes with a fender washer or just slotted L brackets to attach my countertop to my cabinets ? Are they both as good in my situation ?

2. Since wood needs to breathe, it's said that it shouldn't be installed directly over other materials, there should be an "air gap". That is easy with the countertop since the top of the cabinets are open, but how should I design the waterfall sides with an air gap ?

3. What is the best way to attach waterfall edges ? Should the waterfall edges rest on the floor or be given some space off the floor like they were floating ?

4. There will be a dishwasher in the island, should I install a vapor block of some kind, completely seal it or just use mineral oil like on the top ?

5. This is more of a design question : My countertops are 6" wider than what I need (included usual overhang), is it enough for a "bar" overhang or should I just cut it down ?