Your -1 ac, but +1 to dex mod just means that most people put their extra ASI in dex and the game remains unchanged (and, ironically, metal armor is useless to them, because they don't get any benefit from wearing it over the athasian versions).
You can just write back in Dark Sun equivalents, like instead of plate armor there's bug carapace armor, but then you lose one of the things that made Dark Sun feel really different.
If that's what you want, then don't try to make replacements for the metal armors at all. If that pushes people towards barbarians and more agile characters, rather than strength based fighters, then that's not entirely a bad thing. It matches the feel of darksun pretty well.
The effect of that is somewhat countered by the inferior range of 1-handed dex based weapons available.
Are barbarians getting an advantage? No, not really. They're still going to lose AC unless you're playing with crazy high stats. Any barbarian with an ordinary starting array should have been wearing medium armor... only now all the worthwhile medium armor is gone. Barbarians who go dex over strength will be hurting their rages.
I think that removing all the metal armor options and then going through and adding specific athasian armors is probably the best way to go, making sure that the table has gaps where the best armors used to be. That will make people want metal armors, because they will be flat-out better than what's normally available.
The weapons table, you can probably get away with reducing die sizes on all metal weapons by 1. That hits dex users hardest because almost everything they might want just happens to be a metal weapon... but they're avoiding the loss of heavy armor, so it balances out somewhat.
That still won't make metal weapons desirable, since most characters will just use weapons that avoid the penalty. I think if you want metal weapons to be something people covet, you need to add something to them. Personally I would just make any metal weapon +1 or more, and handle the price as normal for magic items. Not that it matters: darksun is one place where the concept of buying and selling rare items really doesn't make sense.
[MENTION=6716779]Zardnaar[/MENTION]
One other thing that I feel you missed: you really need to go through and rewrite all of the lifestyle rules and descriptions. At present roughing it in the desert with the survival skill is giving you a comfortable lifestyle! I also feel like the lower lifestyles probably need to be made much more nasty, and potentially the lowest lifestyle should mean that you're not always getting enough water to live on.
