Would you consider just being happy with the 1.050 (should give you somewhere around 5%) pale ale? That'd probably be your best bet. The 'style guidelines' for an American Pale Ale say you should be between 1.045 and 1.060, so your targeted 1.075 is high anyways.
If you really just want to increase the gravity for the sake of a higher ABV, you're going to need to make some significant additions. If you've got it, go ahead and add enough DME to get the gravity up to where you want it. Alternatively, you could add sugar but, for the amounts you'll need to add, your beer is probably going to turn out very "thin".