If your router reports FEC errors, it would be useful to post these up too. If not, no worries. The FEC (Forward Error Correction) count will tell you how many cells have been corrected by interleaving. If this number racks up considerably then I would leave it on, if this is low then you could probably get interleaving switched off.
Note that switching interleaving off won't really improve your sync speed, all it will do is to reduce your latency or "ping" - if you're not a gamer it's pretty unimportant (and I reckon a lot of gamers conveniently blame their ping time on bad performance - but I probably shouldn't say that cuz it might start a flame war heh
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What's probably happened with your speed is that BT's DLM (dynamic line management) has bumped you up to a higher SNR margin (I note yours is currently 10.5dB) which means your sync speed will be lower.
As regards switching on and off, like Astral says, don't do it too often. I would doubt whether you really need to do it at all, as the automatic DLM might consider it to be a fault, and raise your SNR even more, causing your sync to drop further... which you don't really want to happen!
What router have you got? You might be able to play with a thing called the DMT tool which enables you to adjust your target SNR margin (useful only if your line has been bumped up due to a fault that is now fixed but your SNR is still too high - if your line is unstable there's no point lowering your SNR as it will just get bumped up higher eventually).
Hope that helps
