I've also been thinking that Hana's kidnap was staged, though I don't know whether by TN or someone else.
I don't think TN's husband is the killer, or that TN is (I mean, I do think she killed Tim, but not the women).
At the moment, I"m inclined to think she's misguided about Michael Farmer rather than deliberately fitting him up - she thinks he's the killer, even though he's obviously not. I think she probably killed Tim in a struggle, though that is slightly implausible, given that she's obviously smaller and weaker.
Agree that the whole 30/13 business will be her undoing. The person who wrote 13 on the bag will remember quite clearly that he never wrote 30 and crossed it out.
I don't know why Tim had a balaclava, but I don't think he was the killer. Possibly because he was spying on people and doing his own private investigations.
By the way, in an increasingly implausible (though still enjoyable!) series, the thing that really baffles me is how Kate manages to keep on going undercover and no-one recognises her. This time the new SIO actually knows she's undercover - how long before he tells someone?