Yes, I would like to use my half action. Since both spellcasting and banishing are complex actions, I can't do either of those in this pass, so I'm going to an assensing on the spirit to try and determine what type it is (from what I can see there are two types with noxious breath), what force it is, the link to its summoner (so I can try to find him) and anything more.
If it's a spirit of air, I think the easiest is just to stunbolt it back. Spirits have only 1 condition monitor track and materialised spirits of air have not much body. Also his immunity is against normal weapons, so not against spells.
As to the rest, I'm not sure if I can remove conditions. I can't heal stun damage (heal is only physical) and I don't think I can take away the nausea.
@Crossbow: Sammy has her respirator on (since she has asthma, she almost always wears one against standard pollution). Just so you know as that gives extra protection against the noxious breath.