I also had Palm m515 and DateBk in the good ol' days. If you have iOS device, try Pocket Informant. This is what I use now and I think it covers most, if not all, of your requirements and syncs with toodledo and google calendar too!
I have to admit though, I'm kind of scared, because it appears to have the same level of detail that DateBk did.
I purchased the new version of DateBk called Pimlical for Android and tried it out today. Not quite there but definitely a possibility. Since I'm on iOS I'll try it out.
If this works, I can't begin to put in words how indebted I'll be fore the reco