Well, thanks for the game! I think most people don't realize how much time it takes to make a game of this quality, so publishing it for free is something to honor.
I didn't even know it was based on a particular game family, so I guess your design choices make sense. However, keep in mind that implementing such a game from scratch is a great opportunity for you to add your own touch and features that weren't possible or weren't thought of at the time. I'm pretty sure adding things that make it more comfortable for the player wouldn't damage the nostalgia trip (considering how everything else is well set up).
About the time things, if you tested and came up with these values, then I think I can't argue much about it. But in my opinion, there are two different "too easy" for the player. The first "too easy" would be if the player completes a puzzle by chance or if the puzzles are too obvious to figure out, this one, of course, you want to keep it away. The second "too easy" is when a player figured out a hard puzzle or found the solution to a hard problem, and then isn't struggling to achieve it "mechanically" (clicking something that is too small, too fast, navigating in a slow UI etc...), that kind of "easy" is something you want. Not having it would only be great for action games in my opinion. It felt a bit weird to have to do "come and go" to pass time by 30 minutes instead of just clicking a button. If it was intended to have to figure out the "move, freeze, come back", maybe design a puzzle specifically to have to do something like this (e.g. you can't stay on a tile or you would die from quicksands or something...). Because once the player figured this out, if he has to repeat this task multiple times at other places, you will bore him (pushed to the extreme, that would be like having to cross the desert manually everytime, but you identified that it would be boring and implemented the second kind of "making it easy"). Also, I would undoubtedly prefer a "choose the time spell" with a very long animation over a fast "6 hours forward", this way I would only be able to easily do what makes sense and won't "bruteforce" the solutions. Anyway, I'm pretty sure you have your reasons to design it this way, but just sharing some ideas here.
I haven't played any of the games you mentioned. I've played all the monkey islands, runaways, day of tentacle and this particular king's quest I talked about (also some other indie games). I'd say I'm an experienced gamer and game designer in general, but not particularly in those kind of games.
I saw you made another game of this kind, I felt more attracted to the universe of this one, but I might try the other someday ;)
Also, I edited my other comment and added 2 more things. See ya!