Great job! I can also be a perfectionist when it comes to this stuff, so I know the feeling. It can be hard to just get on with it and try things without having it all figured out ahead of time, but hopefully this showed you that you can do it!
As far as cards goes… I would NOT recommend the Ben System as your next step. It is a very advanced system that requires learning an image for every possible two card combo in a deck of cards. Over 2700 images. Given what you said about the time it took to get comfortable with a partial 2-digit list, I think a more moderate next step would be wise.
If you’re really interested in trying cards and you’re already familiar with the Major System, you can use that technique to create a set of images for cards. You can even use what you have of your existing 00-99 list.
More info here:
Example cards via major system list:
If you want to just experience the cool almost magical feeling of being able to memorize a deck, there is a very simple method that won’t really win any speed prizes, but is almost sure to work. Check it out here:
Whatever you decide to do, keep the excitement level up and try to look at the next step as a brain exercise, personal challenge, whatever it is to stay motivated.