It could be a bad kit, there are plenty of bad kits and recipes that we all end up trying.
But, one week is a little bit on the short side for fermenting. The over carbonation could be that the yeast didnt have time to fully convert the sugars during fermentation, which would lead to more yeast action in the bottle (carbonation) as well as a sweeter final beer (higher FG).
Did you take multiple FG readings? Generally, it is wise to take two to three gravity readings a day or two apart to make sure the final gravity is stable prior to bottling.
To summarize: Try a new kit, ferment for 3 weeks, take multiple gravity readings at the end to ensure the yeast is done.