Unused Fastpass and tiers ques & itinerary help

[dspads]

Wow, I am finding this whole FP+ thing so difficult. We are heading down in August and I have a few general questions:

• What happens if I have my 3 FPs set in 1 park and don't use the 3rd one? Can I book a 4th (same day) and can it be for tier 1 in Epcot?

Example
9am Soarin
10am Spaceship Earth
10:30 Turtle Talk

When can I book my 4th FP? After checking in for TT? What if I never check in?

• If I only book 2 FP in a tiered park, can I only book a third in a different park (same day)?

• If I have 3 FPs in one park, when can I book my 4th?

This is my current FP itinerary and ADRs. We are staying at SSR, will have a car, and don't plan on making RD, but tend to be up early-ish. I figure if we make it to the park before FP times, maybe we can hit a ride or 2 with short wait.
8/16-arrival day - no parks
8/17-MK 10am Splash, 1145 Buzz, 2pm 7 Dwarfs 2. Evening at AK for ROL & dinner at YY
8/18-Waterpark, MK late afternoon HM 440, Pirates 540, SM 825 Wishes
8/19-HS Toy Story 1015, Star Tours 1115, pool afternoon (dinner at hotel or Springs) TOT 8pm, Star Wars fireworks
8/20-AK Kali 925, Safari 1030, Everest 1135, Epcot afternoon/evening try for FPs, Dinner Via Napoli 530
8/21-Waterpark, Epcot late afternoon Soarin 510, SE 610 Dinner R&C 720, Illuminations
8/22-HS RNRC 930, Star Tours 11, not sure on rest of the day
8/23-Epcot TT915 not sure on rest of day

Any advice or thoughts on this appreciated! I am especially not sure what to do the last day as far as book FPs or not. Not sure of the availability will be for same-day FP at this time of year.

Help!!

 

[hiroMYhero]

Here's info on park hopping regarding when you can book and Tiering:
http://www.disboards.com/threads/fp-and-park-hopping.3514422/