You are correct on all counts. The 6561 can only generate frequencies of 200MHz/N with its onboard clock. You could get 40MHz or 33.3MHz, but not 36MHz. You can connect a 36MHz clock source to CLKIN and use that as your sample clock source. You can also export that clock with your data (if you use the DDC Clock Out terminal, the data and clock will have a guaranteed phase relationship).