I think you've basically nailed it.
I make the legends SIGIS(mund) 3 D(ei) G(ratia) REX PMDL and MONE(ta) NO(va) REG(ni) POLO(niae).
I'm not sure what PMDL is an abbreviation of. DL is probably DUX LIVONIAE (duke of Livonia). P is presumably POLONIAE. M?? The other country Sigismund was king of, though not in 1622, is Sweden.
3 polker (1 kruzierz, i.e. Kreuzer) - there is a 3 at the base of the reverse which is slightly clearer on my example, below.
The 24 within the orb is presumably a fraction (there were 24 of these coins in some larger unit). The explanation of the monetary system in KM appears to miss a row of information that should explain the relationship between the polturak and the grosz.