Only thing I can help on is the greys tanks...mine has two grey tanks and each are 22.5 gl. You can't bleed one to the other either (though I'd think it could be set up to work that way). The shower/bath will fill quickly...kitchen not so much.
Ladder wise...several threads on here with what folks have come up with so just search for the words "bunk ladder" and you should return more than a few.
Congrats on the trailer too!
2014 Ram 2500 Laramie, 4X4 CC, 6.4 Hemi, 3.73
2015 Jayco White Hawk 28DSBH Summit Edition