For being "pretty much" a One Player battler, you're taking the Two Player route about your stats and set. There's nothing wrong with that if you've decided you are going to go that route, but as long as you're focused on One Player you should only be keeping the thought in the back of your mind.
First off, the species debate: unless I'm mistaken, Bag of Healing Dust is currently going for 7 mil plus. H4000 Helmet and Freezing Potion are cheaper, and the total cost of morphing to Kacheek and going with the
Kacheek Life Potion is still cheaper.
Even beyond that, in strict One Player battling a healer is not necessary. You can do more with more HP, Drain Life, and Regeneration. In Two Player, on the other hand, you'll need a 50% healer.
You're only running two (real) weapons: Fungus Ray and Ring of the Lost. You're covering five icon types with these two, and you're very likely to find a part of that being blocked. You should be consolidating your icon types, and have more diversity available to yourself. Depending on your budget,
Bow of Destiny,
Scuzzys Comb, and
Essence of Esophagor are the three weapons to look at (and you'll want to dual one of them with a dual of another as backup). You'll either be able to get your full attack through regardless, or be able to get through a full attack with your backups (in the case of the Bow, if you're just losing Fire then you're still averaging 10 each).
From a Two Player standpoint,
Wand of Reality is better comboed with
Pirate Captains Cutlass than any strategy that can be used with the Bow. Something to keep in mind (though the Wand overlaps Light and Physical with the Combs, which would force Essences as backups to it). On the other hand, the Bow can pummel Sink.
Toss your Leaf Shield into your SDB, and sell your Winged Scarab (possibly upgrading to
Yooyuball Player Sling, which is probably very inflated by now). It's not effective because of your high Defense. The Honey Potion is more useful in Two Player, and from a strictly One Player standpoint could be sold for the cash.
Why are you even looking for Fire Defense? Just because of
Portable Kiln and
Mask of Coltzan?
Personally, I'd recommend deciding now whether Two Player is going to be in your (at least near) future. If it's not, just keep training your Defense (for the possible "maybe someday"). Your budget is also much more open if you rule Two Player out (at least for the time being). If not, my advice would be a bit more specific rather than having each point dependent on which route you're taking.
Also, there's a chance this won't come out clearly since I'm typing it when I should be in bed.