I have a scale so I will be able to measure out my corn sugar. I think i ended up with about 4.5 gallons (spilled some on a failed wort transfer with a funnel.) so should I use 3.5 oz or so of corn sugar?
1oz/gallon is sort of a generic rule of thumb, but I prefer to carb more to style and use this calculator as a jumping off point: TastyBrew.com | Homebrewing Calculators | Botting Priming Calculator
It also takes into account the temperature of the beer when you're bottling, which can make a big difference.
That's what it would be, carbonated to style and taking into account the temperature of your beer. It's all up to personal taste though. If you like your IPA to be a bit more fizzy than standard, there's nothing wrong with that.
I gotta agree, I only used the generic rule for my first brew or two. Taking the style and temp into account led to better results for sure. It may seem like too much to too little sometimes, but it usually comes out in the end. (I use BeerSmith's calc, not tastybrew's)