On another front, I wanted to let you know that I don't think you were lied to at all by your initial guide about upgrading your DLR AP to a WDW AP, but more that you just misunderstood.
You can indeed upgrade your DLR AP to an AP that is valid at WDW; however you cannot upgrade to a "WDW AP." What you need to do is upgrade your DLR AP (which is called either a SoCal, SoCal Select, Deluxe, or Premium Annualpass) to a Premier annual pass. The Premier annualpass is good at BOTH the two parks at DLR AND all the parks at WDW. That is what your initial guide was telling you. And, at the time, he told you the correct pricing. So he did not lie to you about that, nor give you incorrect information.
Ooh, good catch. I would HOPE that someone with an AP at one park would know about the both-parks AP, and not think they could just switch it over, but maybe that's what was going on.
I remember having a conversation with a CM where I was asking xyz and he was saying abc, and neither of us could figure out what the other was talking about, and as it went on, what the other was getting upset about. Thankfully no one rushed off in a huff, we kept talking, and suddenly the lights went on for us and we were able to translate what the other was saying. Turns out no one was wrong and no one was right, we just weren't using words that meant the same thing for the other one.
Almost seems like a similar situation. The OP says WDW AP, meaning just that...the rep hears the words but translates it into WDW/DLR AP, doesn't clarify b/c it's so obvious to him, gives the right info. Later the OP uses WDW AP with MS, MS doesn't translate it so easily, says "no" but still doesn't give FULL info, that there's another level of AP, so the OP goes away thinking the upgrade isn't possible at all.
Just as likely your guide didn't understand all of your issues as well. At the end of the day you're in the same place you were when you posted initially. You own a timeshare you don't understand very well and that may or may not work for you. I wonder where you're psyche will be if you find it's not a good fit for you once you truly understand it, I truly hope it works out for you.
I agree. Hope it works out, but not sure the OP totally knows what they bought. Even I with my obsessive research ahead of time missed understanding one thing our guide (who was pretty awesome and I miss him being our guide but he left the company) said. Luckily that was one of the things DH did understand from our conversation, so he was able to explain it before I contacted our guide.

If someone who researched had a blank spot in understanding, it's easy to imagine lots of non-researchers have bigger blank spots.