At this point is there a Jr. B team that wants him as a workhorse no. 1 for the rest of the season? If not, I really doubt an extra 8-10 games more (than he would playing here) in a lower league will be better than continuing to practice with OHL calibre players and play occasionally.
Going from practicing and playing with OHLers for half a year, then going to a different team in a different league more than half way through...what benefit, if any, is probably negligeable.
If the boxer doesn't teach him about where his skates/feet should be on the ice to maintain balance while throwing or dodging, I'm not sure it's going to make much practical difference. He's a tough kid but gets spinning around too much.