@Sonderjye,

Design 1a and b could both work, but b would be more cost effective, but also a bit more complicated to build. There's something about memories that make them easier to move around than to directly copy, so you will have to work on a method to retain the memory in the original crystal while only transferring a copy to the storage crystal(s).

2a is definitely possible, and you've already got some concrete ideas for it based on your current design. Since time elapsing seems based on the experience of the one that made the memory, you think there should be ways to fake a 'bored' or 'interested' state for speeding up ans slowing down. Pausing should be fairly easy as well, skipping with accuracy would be more difficult. If you can find a way to split the subconcious part by sense you could also design a way for a user to activate or deactivate the extra information of the senses you're looking for.

2b is theorethically possible, but editing a memory, especially in a way that looks somewhat believable is going to require far more effort than just rewatching one (it's the difference between making something that can play a film, and designing something that can edit it, and unless you have a massive database of memroies to draw on, you'd need a way to create new bits of memory from nothing). This is definitely something that's more long-term.

3a and 3b are likewise theorethically possible, but more difficult to achieve. If you where to ask your new elvish friend he'd explain that the way their methods work allow them to see the integrity of the mindscape as whole, but they can't really see the contents of any individual memory, beyond getting a rough impression of how long ago it was made, and how big the memory is. Your device can capture specific memories because you personally push the memory in question the forefront. You'd need a fairly quick method that could actually read someone's mind and then determine which bits of a memory are relevant, and which aren't, which isn't exactly trivial.

You've got some ideas about how you might be able to store basic impressions (like tastes, or sights, or smells) this way, but a potion with a more complete memory, while possible, won't ever be cost-effective enough to be able to sell it as a novelty drink ( or at least, not for the next couple centuries).