I think the platforming controls could have both W and Space be for jumping, but the more important fix is probably the physics and precision of the jump, coupled with possibly larger blocks to mitigate the ease of overshooting or slipping off after a jump. With those fixes, it would probably reach a good enough state to be mostly comfortable.
As for the copy-paste controls, no clicking might be good. The changes to couple it with would be an always-on tile highlight where the mouse cursor points and a separate visual indicator or cue when something is copied. Paste is visible on the spot, but Copy is visually harder to tell.
IMO, the multi-tile copy is probably best left out unless you plan to expand the game into a full sized one, where many more aspects and possibilities related to the core idea are explored. Not having it actually helps reinforce the trick in the last level, and you would also be trading clarity of controls for a minor convenience feature.
It is an attractive feature from an engineer’s perspective, as it feels like it should be part of the package of features. However, from a design and player experience angle, it would likely bring more confusion than convenience to the player unless they are given ample practice to get used to the basic form of the copy-paste feature first. In a larger game, though, there would be time & space to teach players from basic to advanced features via gameplay as they progress.
What I can somewhat extrapolate from your intention to “complete the feature set,” though, is that you probably either are or could be a very good software engineer. It’s related to the idea of a “quality gene” (as described by Chris Hecker and Jonathan Blow in a forum discussion). Just a fun little observation. Of course, this quality benefits game-dev and many other craftsmanship type fields as well.
For level design, Edmund Mcmillen (Super Meat Boy) has a nice bonus feature bit from Indie Game: The Movie, and Matt Thorson (Celeste) has a GDC Talk on the topic as well. Both can be found on YouTube, in case you’re interested.