Give them a call, there's a phone number listed in the support section of your account. You'll get a quick answer by doing that. They might be clueless... but at least they answer their phones quickly & try to give good answers.
Ad groups are limited to 10,000 terms. Break your list up into 2 different ad groups and you will be fine.
Are you sure? I am not the most experienced with adcenter but its just telling me I can put there max 2k keywords per adgroup. Did I miss anything?