My problem is I didn't pay attention to the alchemy tree till level 48. Now I'm at level 50 and started to realize the alcehmy tree can make my potions and weapons stronger. My question is can you take more than one 50% foritfy smithing potion and then make weapons at a forge? Will that make the item I'm producing stronger than 100%? Basically can you stack up on potions to make better items or can you only take one 50% smithing potion and not any more to double the effects to 100% or higher?

No, stacking potions like that won't work as dark as I know.

No expert here, but you take the fortify blacksmith potion when you upgrade at workbench or grindstone NOT when you forge. And no, you cannot stack potions. I think with 100 alchemy and appropriate perks as well as fortify alchemy gear you enchant/find/buy you can get higher fortify potions.

How many times can you improve weapons via fortify smithing? What is the highest you can make the armor rating on a weapon?

http://www.uesp.net/wiki/Skyrim:Smithing#Item_Quality