My OGL Paizo Curse of the Crimson Throne AP books are full of
"see MM pg. 59" references for monster stats - ie they are telling the reader to look up a page in
WotC's book, but not using the Monster Manual trade mark. So you can do that under the OGL. They only refer to monsters in the SRD though as the OGL says you can't use the names of 'Product Identity' monsters.
Personally if I were you I'd publish the adventure non-commercially as a fan work. The OGL is intended for publishers and you should not need it unless publishing commercially. Even then you can publish D&D compatible stuff without the OGL, Kenzer did it, but the OGL is generally safest.
