Part of the answer depends on exactly what you're looking your end result to be. If it's just a functional knife, then that tang should be OK. However, you will most likely see evidence of the pitting in the handle/tang joint after clean up. If you're looking to make it look like 'new', you will have to sand the tang flat on both sides at least enough to remove all pitting around the perimeter of the tang. If you do this, I'd go no finer than 60 grit, because the scratches will provide little undercuts for the epoxy to grab onto. (I'd also sand the scales flat with no finer than 60 grit either.)
As far as epoxy, the general rule is the slower setting epoxies tend to be stronger than the 5 minute stuff. However, I recently came across a thread in another knifemaking forum where a very respected Master Smith (from the ABS) commented that he has used JB Weld and cheap 5-minute epoxy over the years and has yet to experience any failures due to his choice of epoxy. In general, a kitchen knife will probably experience less abuse than a EDC, hunter or bowie, so you're probably good with whatever 2-part epoxy you use. Pay attention to the color of the epoxy, you might not like to see a white line between the tang and scale, but you might like that, but the pitting will be more apparent.
Have fun and make sure you share pics of the final product.