I am currently undergoing the ROTP application process for the 2015-2016 year, so I might be able to provide some answers. With that said I would also encourage you to search these forums as your questions have been answered before.
1. You can retake the Aptitude test and they will take the new score (even if it is lower). This does have to be a certain period of time after your first test (which I can't recall - I do believe it to be less than 9 months though).
2. Since you received the email to contact your local CFRC, it means your grades were sufficient for RMC and you should be moving on to setting up your CFAT/ Personality Questionnaire (this is what the appointment is for - in my case anyway). I am assuming you have sent transcripts/academic questionnaire to RMC already?
3. I would caution you now not to get your hopes up. I applied late myself, and I am still uncertain if I could be merit listed in time for the last round of ROTP selections. As another user informed me, DAA, these selections take place 3 or so times during March - May, and after which they may perform "top ups" to fill any empty positions. With that said, if you are successful in getting an offer in the next two months, you would likely be attending BMOQ in the last week of May to Early June (this is what I was told by my CFRC). To give you an idea, take a peek at my signature. I was told that after writing my CFAT and passing yesterday, that there will be some waiting time (could be more than 3 weeks) before I get an interview and medical set up. I was also told that my CFRC is booking interviews/medicals right now for mid to end April. This may be different for your local CFRC but as I say, since you applied so late, don't get your hopes up.
Again, read around a bit, there is a lot of good information already here. Good luck!