having issues with my clutch...when i got the bike the button in the cover was leaking, so i popped it out and replaced the o-ring. it worked fine, bled the master and it was good. Since then i haven't put 10 miles on it, and now the clutch stays engaged inconsistently when i pull the clutch in. sometimes it works perfect, sometimes it walks on me when i come to a stop...im fairly certain its the master, but really strange. i removed the clutch plates to inspect them and see if the hub nut was loose (it wasnt) and the pilot on the back of the plate that is brazed on was cracked around the brazing. is that common? also, is there a replacement brass button for the clutch cover side? and is it normal that a steel plate be directly against the backing plate in the hub?

Have a look at the post re brake bleeding the paso 750 a few below yours as the bleeding issues are the same ( the clutch is notoriously hard to bleed and often the best method is to reverse bleed ... IE force the fluid up from the bleed nipple up into the master cylinder or brake pump ... whatever you want to call it ) , and then have a look at the FAQ's for the 750 re clutch mods and you will see that the later model 907 and SS model clutch pistons can be fitted ( and are better ) with the addition of a bearing and a button , The button can be made out of the correct sized brass bolt by putting bolt in drill and use a file to fashion a dome out of the head of the bolt and then trim bolt shank to slightly longer that the width of the bearing , put newly made bolt/dome into bearing and slightly pein or centre punch end of bolt so it doesn't fall out of bearing ..... before fitting bearing to piston .
There should be a steel plate against the backing plate as you mention and it should ( from memory ) be thicker than the other steel plates.
The local Ducati Guru here tells me that the cracked pilot is common and he just removes it all together , not to sure about that myself . Make sure your plates are clean and check the two oil seals for any sign of leakage and then replace em anyway ( standard sized seals... get them from a bearing supply outfit ... not ducati ,$$$$$) , any oil weeping onto clutch plates will burn and turn into sticky black shit that will cause your clutch to drag and generally be a complete bastard of a thing