If you're planning to do Two Player, you should keep your Defense up. You're nearly two Strength Boosts ahead of it (though more of just a full one, since your Defense is almost to 55, and your Strength is almost to 85). Your Scarab Ring is useless to you in One Player right now (Vermont will come along at some point and disagree with me on that), but your Golden Compass will still have an edge in certain situations compared to normal nine-iconers.
Dump the Essence of Esophagor. In Two Player a Leaf Shield will cripple it, and it's only a nine-iconer. I'd suggest an Ice Club instead, as it (should be) cheaper, and the difference in One Player shouldn't be anything drastic, especially since you already have the Ramtors Spellbook for a ten-iconer and more variety.
Some years back I recall Snowglobe Staff being cited as having a higher Freezing percentage than
Black Frost Cannon, but the current IDB listing is stating otherwise (though the margin of error may throw them back together). Go with the Black Frost Cannon for (what should be) a better chance at Freezing, as well as not "wasting" each turn that it doesn't do something, or does something worthless.
Everything you listed from your SDB, except the Purple Sticky Hand, and maybe the Leaf Shield, doesn't strike me as worthwhile.
Wait, you have 3.8 mil to spend? Hum... I'd suggest training overall, or at least keeping enough money that you can keep up with constant training. K-Quests tend to be expensive at your level (NP to stat ratio, though you can always give them a try), and Faerie Quests aren't around enough to be considered a reliable means of training (definitely wanted, but rarely around).
Train, especially since you're doing more One Player right now, and your Strength Boost impacts that the most heavily. But if you want to do Two Player somewhere down the road, you should keep up your Defense.
If you want to spend all of it on weapons upgrades...
Wand of Reality or
Bow of Destiny (more for One Player), or
Mask of Coltzan (for Two Player, though you'll need your Defense Boost up) are all considerations for "blowing it on one thing." Either of the first two would blend nicely with your set, with Bow of Destiny being my recommendation. Right now your Ramtors Spellbook blasts through Burrow, and a Bow of Destiny would blast through Sink. Wand of Reality would partially blast through either, and make your set a tad Light heavy (though I don't think there's much in the way of Light defense for that to matter much).