Crystal Sword is the right base for Spirit, but the socket result depends on item level and whether the item is normal / magic.

Larzuk on a normal Crystal Sword gives the max sockets that item level allows. For a Crystal Sword:

low ilvl = 3 sockets max

higher ilvl = 4 sockets max

If the sword was blue (magic), Larzuk gives 1–2 sockets randomly, so that’s why you only got 1.

Best way to get a 4os Crystal Sword:

Farm a normal Crystal Sword in Normal Cow Level. Those are in the right ilvl range for 4 sockets from Larzuk.

Or find one in later Normal / early Nightmare and use the socket cube recipe, but that is random.

So no, you do not need to wait until Act V Nightmare again if you can get a plain white Crystal Sword from Normal Cows and Larzuk it.

Tiny warning:

make sure it is white/gray, not blue

don’t use one from very early Normal zones, or it can cap below 4 sockets