Acid wash would grant a +4 save bonus verse disintegration
Folded Metal would grant a +4 to hardness
Resilient +5 Hit points
Ornate makes it look pretty and Serrated causes bleeding damage on crits, but overall the crafter has to have a feat to craft these modification and learns only so many based on his skill. I would focus on Folded Metal and Resilient. There are also very awesome armor mods in that article, more so than the weapon ones.
You can stack all of these with all the previously mentioned modifications. I believe you would first add up all the multipliers and apply that to the base weapon, followed by all the additive values. HP is an arbitrary non-real world value, so I don't think two 2x make a 4x by 3.5 rules (instead a 3x). Hardness on the other hand is a real world value, so I guess it depends if you see it as true hardness or as a form of damage reduction. I would think those multipliers would multiple, so 2x and 2x would be 4x. Please correct me if I am wrong. This would apply to any enhancement bonuses on the weapon as well that add straight hardness and HP.
There is also another spell in the stronghold builders guide called Augment object with a duration of 1 day/ caster level that doubles hardness and HP (plus increases the item break DC by +20). Since this is on the final finished product, it would double everything?
There are also weapon templates in the DMG2, but none are as good as dwarfcrafted and you can only add one template.
I completely forgot the ring was indestructable. My pre-spell plague character feels much safer now (although the spell plague is an unusual event).
Just make sure the 4,000gp ring you start with has properties you don't want since they are forever lost. I don't think re-enchanting it with the same property would bring it back.