Have you tried filling your mags with duster? If the lack of an adapter is stopping you, you can use the one that comes with the can. Here is a vid I shot for a newbie a while ago showing him how to fill a Glock 19 mag, and fire his gun. Its the same basic idea for any pistol mag.
http://ahl.telefragged.com/ace12ga/airsoft/glock19.wmv
The fellows duster in the yellow can is probably the best source of HFC134a, tetrafluoroethane; you want to avoid difluoroethane, as its been known to cause damage to seals. Any can of duster that is tetrafluoroethane will work. Add a single drop of silicone oil to the fill valve before filling, and you're good.
The mag catch thing happens on Glocks too (causing similar problems). The best way to check for it is holding the mag up with your hand when you fire. If your problem goes away, then you need a new mag catch.
With a mag in the gun, can you recreate the slide getting stuck halfway by manually cycling the slide? A last note, the only maruzen I have ever owned was the MP5K, but it has a similar problem when used with green gas. It gets jammed, as well as not cycling properly.