Hah, silly me, I already had a WinAPE savestate at the end of the game. I had 85600 right before I used the potion on Zaks--but it turned out I hadn't visited The Waiting Room at that point, which gave me another 1000 points for a final total of 86600!

Touring the game again, I saw 3 unreachable spiders, 1 unreachable raindrop, 1 unreachable bat, and 1 unreachable extra life.
I was also trying to play this "glitch-free", so I don't know where I would have gone that you missed. I know there are a few blank "sky" screens that are easy to miss, one to the left of the gardener's spade, and a couple more over the mountain. I think you actually had to find another one of these to get the cloud's silver lining, correct?
And there are some points you have to die to get, like I must have put off visiting The Waiting Room because you have to die on the skeleton to get out after falling in, and I'm pretty sure there's at least one stalactite you have to jump into water to destroy. ...Unless you can use the dry ice there, which I haven't gotten around to trying on horizontal pools of water yet...
I can make the score even higher if I use the glitch described in
this topic, but I hadn't planned out re-collecting all those objects and dumping them over the skeleton yet. I wonder why that skeleton works like that...?