There's a good reason it's illegal for handymen to do this sort of work. It shouldn't take any competent person more than an hour to do the wiring. There may be drywall repairs needed as the pendant dome is likely to be smaller than the hole in the ceiling. Of course, there are things on the market that screw into your pot light socket and allow a pendant to be hung there.

a row to the front side, and a row to the back side of the beam should be plenty with the pendants over the island. just put them on separate switches. I could see having three switches, interior kitchen, hallway side kitchen and island.

Juno IC1RLED with 17cwh trim. Merely adjusting the beam spread won’t get rid of the glare. You need a fixture that has the light source deeply recessed so it is not visible unless you’re looking right up at it. The specular clear reflector is the best trim choice - it produces the least glare. White plastic produces the most glare. Black plastic minimizes glare but also cuts a substantial amount of light output. Juno makes a unique hyperbolic trim that completely hides the light source but they’re expensive.

It might seem like semantics, but there are no "rules" of spacing lights. It is based on fixture size, lumens, throw, and the use and design of the space. When you do enough of a design though, basic patterns start repeating for the same set of variables. For a proper lighting layout, I would suggest drawing the plan to scale. Use 1 square = 6" and show thickness of walls. It looks like you are adding lighting to an existing untouched kitchen. So soffits, stove hood/cab above, and cabinet above ref usually act as snags to think about.