I go to the board on Friday. How soon will I be able to compete for cutoff points? I have until Jan 2015 to be promoted.

So you've hit rcp and now you wanna save your ass by Progressing at the last minute. If I was your leadership, I'd let you take the long walk. However, I'm not so...
Before I post my answer, I'm going to give you a little professional development. I don't know what your situation is, but there's undoubtedly some reason why you're still a SPC at nearly 8 years. Even so, your time in service and time in grade (that is permitting your board attendance), you should know these things. If you want to progress to the NCO ranks, knowing this stuff is part of your job. When you put those stripes on, your soldiers will ask you these same questions. You MUST KNOW these things. S1 is not the catch all for soldier questions. Know how to research on HRC's webpage. Know how to log in and view your ppw. On the opening page it explains EVERYTHING you just asked.
On to your answer.
The cutoff is now actually in the beginning of the same month for the points that come out at the end of the month. Points need to be on your erb or processed to your ppw by the 7th last I checked. You must verify that your ppw is correct. The old 3355 had to be certified but the new ppw draws all info off of the erb. If your erb is jacked then your promotion points will be as well. After your board, your s1 will have you verify your info. At that time, ask them to make corrections. If your info isn't posted by the morning of the 8th, you'll have to wait for the following months cutoff scores to be released.

As long as you are in a promotable status, the April board will certify you for May promotion consideration.

if you make the cutoff,you will be promoted 1st of May