I think you have it mostly, except for extra quotes that are not making any sense.
Everybody with a ticket can get 3 FastPass+'s per day. If you have multi-day tickets, you get 3 per day of ticket. If you are staying onsite, you can book them at 60 days. If you’re off-site, you can only book your 3 FPP 30 days early. Also, if you’re on-site, you can book for 10 days of your vacation starting at 60 days from the start of your vacation. You definitely want to book your 3 a day as early as you can.
To get a 4th FPP for a day, you have to use your first 3. That would be the day you are in the park.
If you book them for early in the day, you have a better selection for the 4th and beyond, but no guarantees. On the other hand, crowds are generally lower during the first 2 hours, so some people suggest aiming for the first FastPass at 2 hours after the park opens.