The 'difficulty' scale is a bit odd. By my count you have:
Easy/Moderate
Moderate
Moderate/Difficult
Difficult
Difficult/Very Difficult
Very Difficult
Extremely Difficult
Maybe consider a relative scale, with 1 being 'easier' and 7 being 'harder'? This might make comparisons a bit easier, given that people looking at it will likely have already hiked at least one peak already.
As for suggestions, I would change the following ratings:
Galehead: Easy/Moderate (1/7). Gentle hike up, not a ton of elevation. Nothing technical
Garfield: Difficult (4/7) (. 10 miles, and a good chunk of vertical. Similar to Moriah.
Hancocks: Difficult (4/7). It's a big day in additional to the lack of views.
Lafayette: Difficult/Very Difficult (5/7). Big vertical and lots of exposure.
Liberty: Difficult (4/7). Lots of vertical.
Moosilauke: Moderate/Difficult (3/7). via Gorge Brook, good grades, moderate vertical
Osceola: Easy/Moderate (1/7). from Tripoli Rd. Easy grades and moderate vertical, similar to Tecumseh.
Pierce: Easy/Moderate (1/7). via Crawford path. Easy grades and moderate vertical, similar to Eisenhower, but slightly easier/less exposed.
North Twin: Difficult (4/7). Long day (dist/vert), potentially difficult crossings.
Waumbek: Easy/Moderate (1/7). Gentle terrain, moderate vertical, well protected.
Whiteface: Very difficult (5/7). Rough terrain up blueberry ledges (but fun!). Or lots of crossings on Downes Brook. Lots of vertical either way. I do like this one of newbies though, as the views are word it, and the scrambling is fun, but it's still a very difficult hike.
Your scenic ratings seem spot on, but again I might suggest the 1-7 scale to help make comparisons easier.
As for 'commonly hiked with':
Eisenhower is commonly done with Pierce.
Galehead is commonly done with both the Twins, and Garfield (but as separate loops)
Jefferson is commonly done with Washington.
North Twin commonly done with Galehead
Zealand is commonly done with the Bonds (as you noted above)
I'm not sure how common it is to combine the Wildcats with Carter Dome, it's a huge day, but it seems popular.
AS for beginner hikes:
Carrigan: Yes - the fire tower is worth it. Lots of vertical and distance, but terrain is easy and decently sheltered. Canon, Eisenhower, Pierce, and the Osceolas are my go-to hikes for beginners, so nice work.
Hope that helps.
Washington commonly done with Jefferson as well.