Initial weapons are good enough, but barely imo, and even then, only if you really know what you're doing. I remember getting annoyed at the lack of sharpness myself (not that I'm any good at the game, but I do know what I'm doing a little). Go craft more stuff, it's part of the fun and it'll make your life easier. Good luck!
Went with your suggestion and crafted an iron katana. Not having to resharpen after every 5 hits helped a lot and I beat it without fainting once.
Potions? Mega potions? Hopefully, you mean mega potions. If not, buy some potions and combine them at the chest with honey to make a mega potion. That's more powerful. You can go on a harvest tour to find more herbs, blue mushrooms and honey. And early on, i gather, while I'm hunting, to help build up your chest box.
I was using plain herbs, not even potions '>.>
But I did go into the items menus more heavily and crafted plenty of stuff that helped me during the fight such as potions, flash bombs, and poisoned meat.
Do nutrients (the item that increases total health) last forever or are they only temporary?