I have regular DDP and these are all booked. Is it worth the upgrade? Im afraid it will be too much food! Eating too much. What do you recommend for substitutions. Should I pick and choose now and then wing it down there?

Don't wing it! You're likely to end up dining CS your entire visit!
Here's your list:
8/22 Lunch Crystal Palace
Dinner Artist Point
8/23 Dinner Chef Mickey
8/24 Dinner Trails End
8/25 Lunch 50's Prime Time Cafe
8/25 Dinner Boma
8/26 Dinner Holywood Brown Derby
8/27 Dinner Yachtsman Steakhouse
8/28 Lunch Biergarten
Crystal Palace (in MK), Chef Mickey's (in Contemporary Resort) & Trails End (at Fort Wilderness) all are convenient to MK. Since you've exceeding your 6 TS credits, I probably would drop Trails End by default, unless you really want to dine there.
Artist Pointe? Is that at WL, where you are staying? It might make sense, but I would have only one ADR per day--personally. But that's me! Again, someone mentioned that AP is a signature restaurant requiring 2 TS credits. So you'll need to decide which ADR works better for you.
50s Prime Time & Hollywood Brown Derby are in DHS (Disney Hollywood Studios). Hollywood Brown Derby is a signature restaurant, requiring 2 TS credits. Unless you are using it for the Fantasmic! Dinner Package, I probably would drop it. 50s Prime Time is fun--if you've ever been to Ed Dbevic's, it's the same basic premise. Or, I should say, the flagship restaurant was! I've never gone to any of the other locations!
Boma is at AKL, which is convenient to AK.
Biergarten is in WS at EPCOT, and Yachtsmans' Steakhouse is in YC (Yacht Club Resort), which also is convenient to EPCOT and DHS. Yachtsmans' is a 2 TS credit signature restaurant.
If you drop all of the signature dining, you would still have:
8/22 Lunch Crystal Palace (in MK)
8/23 Dinner Chef Mickey (MK area)
8/24 Dinner Trails End (MK area)****(may be eliminated)
8/25 Lunch 50's Prime Time Cafe (in DHS)
8/25 Dinner Boma (AK area)
8/28 Lunch Biergarten (in EPCOT)
Just noticed you have two ADRs on 08/25. Apart from possibly too much food in one day, you would be running from lunch at DHS to dinner at AKL, which would take a serious chunk of time out of your touring day. I would try to reschedule one of them for 08/24 and eliminate Trails End or on 08/26 or 08/27. Then I would try to book one ADR for one of the remaining two days (eliminating Trails End if it wasn't already eliminated by moving either Boma or 50s Prime Time to that date).
Some suggestions for ADRs that aren't always booked as quickly as some of the other TS restaurants:
Turf Grill (at SSR--Saratoga Springs Resort)
Captain's Grill (at YC--Yacht Club)
The Turf Grill would have the advantage of being up the river from DTD (Downtown Disney). You could plan to spend a day--or a good portion of one!--at DTD, then take a ferry (more a water taxi, really) to a meal at the Turf Grill.
And Captain's Grill at YC is very convenient to EPCOT--you can take a Friendship boat from the IG (International Gateway), which is the EPCOT resort area entrance to WS. You'll probably need more than one day at that park!
That would leave you one day without an ADR--which is not necessarily a bad thing on the DDP! *LOL*