The longest words you'll make out of those letters are camp, coma, comp, capo
Breeder is a 7 letter words using only those letters
You can not spell any 4 letter words with the 3RD letter N using only the letters pmhlijkssxt. The letters do not include the letter N.
There are three 7-letter words possible:roosterrooterstoreros
'PROSCENIUM' itself is the only 10-letter word using those letters. There are several 8-letter words, but no other 10-letter ones.
sultana
snowday
hipster
estuary
pluvial
failers
Beanbag
alpaca