Ok. I just reread through this thread. You are correct about allowing aeration to bring the ph without raising the alk at the same time. Your alk at 140 is fine. I wouldn't worry about lowering it. Go ahead and retest ph. If it is below 7.0, I'd bring it up with some more Borax as you have been doing. If it is at least 7.0, you can just continue aerating and it should come back up. If it does not, then you can add a little Borax.