Soul crystal only advises on story progression, it is not a help in many instances, like k-pages. So you often may get SoulCrystal just telling you finished update, while your game still has undiscovered items.
According to your writing, attic key is unrelated, as I visited Alia's attic long time ago.
So how many updates back I should look at HHA videos to get idea how to open it?
This has the earmarks of someone who has recently joined in progress rather than having played through from the beginning, but I'll play along.
As Omnikuken (twice) told you, the attic key is for
the chest in the bar's attic and, if I remember correctly,
contains a dart board for your game room at the house. I'm not sure whether this shows up as an extra in the soul crystal stats counter but, you've been in the
bar's attic, so you would've seen the
chest right in the middle of the room, no soul crystal or board pollution necessary.
As for the wall you are facing, as evidenced by the rock bomb recipe still strewn about in the park, the story intends to give you more of them- just not yet. The only other times you've secured the necessary nitroglycerin, it's been though the doctor. You can be reasonably certain that, when the time comes to blow that wall, the story will take you to the doctor's office for more nitroglycerin.