The pumping of the pedal and long recovery time are normal when that happens. Often the only way to fix it is to bleed the brakes. I would not be concerned.
As far as your braking technique one thing I always like to teach to my students is to use the full effectiveness of the brakes. Most people are so used to driving on the street that they don't actually know what their brakes are capable of and such don't brake hard enough on track. The exercise I use to teach them how to get used to braking on track after they are used to braking too easily on track is to have them keep the braking point the same , as most people are worried they won't make the corner hence the early braking, and to simply mash the pedal as hard as possible until engaging abs. This will result in the car over slowing and stopping much more quickly then they are used to. After a few times of doing this they realize the brakes have plenty to slow they car and we start pushing the brake point further.
As a means of comparison. I often track my 335 when I don't feel like taking my race miata. It makes 400 whp and weighs 3500 pounds. Much more power and much heavier than I would assume of your car. I run stock brakes entirely except with hawk hp+ pads and motul rbf600 fluid and rarely have issues.