Welcome to AW! To answer your questions: don't sweat your degree being non-technical. They aren't looking for exclusively technical degrees for INTEL; that's more strongly considered for Information Warfare (IW) and Information Professional (IP). There are INTEL Officers with a wide variety of educational backgrounds. Low GPA can be mitigated by positive performance in other roles in your life since then. Also, many applicants do have graduate degrees; that's another thing to consider if you don't get selected right away. Your desire to serve as an enlisted Sailor will also be looked upon favorably (does your command know about and support your pursuit of a direct commission?).
I have witnessed a good number of law enforcement officers have success at the board...so that kind of experience is also a positive. The one thing you may have trouble with is the lack of leadership experience. The direct commission process is looking for individuals who already have demonstrated leadership experience. This doesn't have to be in a job, but could be through volunteer work, extracurricular activities, etc...so look for ways to highlight that, or to enhance your experience in those areas. Again, it doesn't have to be through your job.
I think most interviewers understand that applicants may be nervous; check with your recruiter or the Police Major friend to see if you can get a feel for how you did. Your interview is literally scored, so they should be able to give you some kind of subjective idea about how you did. You are allowed to submit a package after six months has passed since your formal notice of non-selection. You can apply sooner than six months, but something significant in your package needs to have changed, and a letter of reconsideration needs to be submitted along with your package. There is no limit, per se, as long as you have an Officer Recruiter willing to continue to submit packages — but you also need to have fresh interviews, letters of recommendation, etc. (e.g., less than a year old), so it's not just as simple as putting the same package in each time.
This instruction is a very good overview of your whole process, from your recruiter's perspective. It should give you a good idea of the mechanics of everything, and help to make sure you're not missing anything.
As to the quotas, I don't know how many slots there will be, but I can give you information from the last three boards (quoting myself from elsewhere):
SEP 2009 - 176 total applicants. Selected: 57 INTEL (last INTEL-only board).
MAR 2010 - 278 total applicants. Selected: 31 INTEL, 11 IW, 13 IP (first joint IDC board; this board was where all of the FY10 quotas for IW and IP were selected).
SEP 2010 - 262 total applicants; selected: 41 INTEL, 10 IW, 5 IP, 2 METOC.
MAR 2011 - anticipated to be INTEL-only to fill remaining FY11 quotas, but I have also heard a rumor that this board may not even be held, which would push the next board out to the SEP 2011 timeframe. Please do not take my word for this, but I know how it is to be anxious for information, so I'm passing along what I know.
Hope this helps!
