The screen exists but it's pretty easy to miss. I found it my mistake. To see your stats, click on the inkwell icon (second button from the top) and on the right side, click on the white "Skills" text (from "Stats / Skills").

From what I remember, the attack and defense skills always remain 0/300. You can't increase them. You are probably talking about the "atck" and "def" stats which increase based on your stats and equipment. Those work correctly.

Revenant is a rushed game. It has a lot of bugs and partially implemented features. I believe it was never playtested from beginning to end. It is very hard to finish due to various missing quality of life features. I remember looking through the code/config and seeing that health, mana and stamina regeneration should have been percentage based, but it the final game the regeneration is just a flat amount that doesn't scale with your level.