I think you are somewhat confused about the updates and weapon drops
In this game there are 3 way to acquire weapons:
- From Quest
Some weapons are given when completing a quest, some of those quest make you choose what weapons you want, in that case the second time you are doing the quest, the other weapon you didn't choose is given automatically
- Enemy/Chest Drop
Some enemies, especially certain non mandatory bosses, have unique weapon drops when you kill them, check the achievement screen to be sure to have found and killed them all
Other weapons are randomly dropped or found in chest, to get those you'll need to continue playing, there isn't an exact location where such weapon are found
- From The Weapon Shop
A few weapons can be brought from the weapon shop later in the game, make sure to have enough Z to buy them if you are interested in them
I found all 75 weapons in this game, or at least i think i have, and it took me 3 play trough including the final boss to get the last sword, you can't even have all weapons without finishing most of the game at least twice due to quest weapons reward, and don't worry, eventually all weapons are found, sooner or later
Only exception being the razorback as it's a preoreder bonus, and the gold weapons variation that right now are given only on a complete new game, not new game +, that may change tough now that the upgrade is avaible
As for the orbs, check the official update log to see what they are for:
- After finishing missions for the second time, instead of Skill Points the player now receives a powerful new currency called 'Orbs of Masamune'. The number of Orbs depends on the difficulty level. A new set of violent challenges will be added to the game soon. Players finishing these challenges will be able to imbue Smith's Anvil with power to greatly improve weapon stats. Orbs of Masamune will play crucial role in this process.