[Mithadan]

Boldog, as a name at least, appears early on as a great captain of the Orcs, if I recall. I just finished both Beren and Luthien and The Fall of Gondolin and I took note of a mention that Boldog was slain. If I had to guess based upon memory, I would say it was in the Lay of Leithien.

It is not clear that the breeding of Orcs began after the fall of Utumno. This would mean that the task was left in other hands (Sauron perhaps) or that the breeding began after Morgoth returned to Angband, leaving too little time, in my opinion, to create the armies described in the Silmarillion. Because the corruption of Orcs (and I will not be dragged into the Elves/Men/Beasts discussion) is clearly attributed to Morgoth, I would guess that the breeding program at least began while he was still in Utumno.

While Maiar were clearly recruited by Morgoth, their numbers are not clear. Certainly the Balrogs (hundreds per the Lay of Leithien, seven per later notes), and probably all speaking monsters including dragons, Draugluin and Carcharoth.