Your check-list is very good. That pretty much covers the main things it's important to look for in single cards.
Regarding combos, it probably seems like a lot of memorization, but not as much as it seems. Once you've used a particular combo successfully, it'll probably be second nature to you: you'll remember your success with it and probably not miss it the next time it comes up. You only tend to have to memorize combos before you've actually used them.
More significantly, however, is that you don't need to know all the specific combos (of which there are far too many to memorize), just the types of combos. For example, Mining Village/Rabble is roughly the same engine as Farming Village/Torturer. You don't have to remember all the different combinations of villages and drawers, just that you can build an engine out of one of each. Some instances of this engine (Fishing Village/Torturer) are better than others (Village/Smithy), but you can evaluate any given pairing on a case-by-case basis once you've spotted one in a kingdom.
Another example type of combo is "hand size increaser" plus "something that's more powerful with a lot of cards in hand." This could be Tactician/Coppersmith or Laboratories/Bank or something like that. Spot one piece in the kingdom, look for the other.
Another one: "thing that wants another specific thing in your hand" (Tournament, Baron, Treasure Map, Fool's Gold) probably all combo nicely with "thing that improves your hand" (Cellar, Warehouse, Laboratory, Stables).
Strong attacks are definitely important to spot, as you've noted. But upon spotting an attack, check to see if there's a defense for it. Once again, it's not important to remember specifically that, for example, Farming Village is a good counter to Rabble. Instead, you can just remember "top-deck manipulator is a good counter for top-deck junker." By remembering that one rule, you can recognize a wide range of individual combos: namely, that if Rabble, Bureaucrat, Sea Hag, Fortune Teller, Spy, or Scrying Pool is on the table, any of Farming Village, Cartographer, Scout, Navigator, Jack of All Trades, or Lookout is probably a defense for it.
Once you get a feel for the types of combos to look out for, there isn't much left to memorize, as there are surprisingly few combos that are truly unique (Native Village/Bridge being one). The more common categories of combos are what's important to train yourself to spot, and like I say these start to become second nature once you've been successful using them in practice a couple times.