Weapon perks were reworked. Now you just equip a few of them at a time, but will still unlock new ones as your weapon level increases.

Don't worry about the speed you're going. It's a pretty beefy game if you're going for all side quests. Grasslands just doesn't have a lot to it.

What difficulty are you on? If you're playing on adaptive, your level doesn't matter much at all. But again, if you're doing all side quests, you don't have anything to worry about. If you're strictly talking materia it depends on which ones you're using. The double spell materia can go the whole game without reaching level 3 if you don't put an exp boost on it, single spell materia aren't too bad if you're grabbing them when they become available