Definitely go with circumin. As for the IBU, in that low dosage I don't see there being any big negative side effects. It would help decrease the inflammation, so it is arguable whether it is masking the issue or helping with recovery. On one hand, you are not fixing the issue that is causing the inflammation, but on the other you may have an issue that you can't fully remove without invasive intervention (bone spur, etc).
I will forewarn with this though - I have worked with athletes in the past who have said "I will just take it before games, etc" but then end up slowly increase the dosage and frequency of taking the IBU. So just be sure to stick with your merits and limit you consumption to what you plan. Also, do not neglect the other stuff that you are already doing - foam rolling, straussburg sock, mobility drills, etc. I would also begin a compression (and ice if you feel it helps) regiment post training as well.
Take a look into traction therapy as well. I have found some great results with chronic ankle problems by using traction based therapy. The book "Don't Ice That Ankle" gives some great insight into the reasoning behind the approach and gives examples of how to do it on your own with some jump stretch bands.