Nice looking layout, Tom. I’ll try to answer as concisely as possible.
1 Yes (that’s concise )
2 Yes. You can use fiber pins to isolate the center rail on any leg of the switch. Just keep in mind that one of those legs needs have a metal pin to supply track power to the switch.
3 It dosen’t matter how you power the switch but, since the other switches have a constant supply, I would stay consistent.
4 A block is just a section where you have isolated the center rail so that you can stop a train. Your controller with the spur control is essentially a single pole, single throw switch (SPST). That controller should be used in conjunction with the switch(es) that connect that siding to the layout. I’m not totally sure that is what you are asking.
Hope I helped. Happy Holidays!