The Rynjin Sentries have utterly obliterated my party twice with what seemed to be Shrill Sound spells. I might need to level up first. I killed the first band with the Overseer and 3 Thralls easily. But this group seems to be on another level.

Oh, and my Alchemist is insane. I thought it would wear off but its not. I might be able to win if I can get him normal again.

Are you using Magic Screen? If not, do so, and try to use it at Power Level 7. To learn it, raise your Valkyrie to level 9 and her Divinity to 30, then buy the spell from Lord Braffit in Arnika. (If he doesn't sell it, try resting 24 hours.) This spell can't backfire, and (especially at higher power levels) it lasts a long time.

There's also Element Shield and Soul Shield, but those only protect you during the battle you cast them, and they can wear off in longer fights.
Is your Alchemist, by any chance, carrying the Destinae Dominus?

If not, try having her drink a Potion of Restoration outside of combat. If so, you need the Helm of Serenity.

As a temporary workaround, you can put the Destinae Dominus inside a container, like one of the lockers in Arnika's jail. Of course, you will eventually need to retrieve it. (Don't put it in the Rapax Away Camp, as that could get you permanently stuck.)

there is a spy in the Umpani camp... plot twist ...you can avoid the spy but the other work around (hand her items) is better ime

Also, if you have played through that subplot before and know how to expose the spy, you can get a rather large amount of experience (250k IIRC) early in the game, but I wouldn't recommend it for two reasons, one of which is level scaling and the other would spoil the subplot.

Putting globe artifacts into containers is usually a bad idea. The game tracks your game progression based on how many of them you have in your inventory, not how many you've FOUND, so unless you stash them immediately after getting them, you can create a bunch of weirdness. You can mess up the various harassment patrols and the landslide on Ascension Peak as well.
The only way to get the Destinae Dominus without having the Helm is to kill Marten for it, so if he's having trouble with the sentries I doubt that's the source of his problem anyway.

Activating Z'ant with artifacts is a good workaround, but I'm pretty sure you can't get the final quest in the chain that way, because that quest is given by the greeting (which is overridden by showing the artifact). I can't remember if it interferes with any of the Away Camp business, though. I find the fact that He'Li offers a bribe but it has no effect on the discovery chance to be a pretty annoying bug. For my game, I used the Cosmic Forge editor to blank out the conditions on Z'Ant's betrayal dialog to prevent it from showing up, and I simply make a point of paying He'Li as quickly as possible.