About your L10n and i18n codes, a resent tip is going around: you should use a string instead of self::dom as it makes the automated tools work for translators.
Do you have an email, or contact form that I can send you a possible way that the reCAPTCHA check can be bypassed? I haven't tested it, but it looks to be possible from your code, and I'd rather not suggest how to do it on an open forum.
By the way, you plugin is by far the best coded reCAPTCHA plugin that I've found. Thanks.