Not sure which stash you mean. There are 2: your personal and transfer stash shared between characters. For both you can buy additional tabs if current ones are full. If you did that and even with all tabs unlocked your stash is full, then this is an intentional constraint the game puts on you. You can either deal with that or… use GDStash for infinite stash.
As for attributes - with my current character I split points like 40 % physique, 40 % cunning, 20 % spirit and have lots of fun. It’s up to you.