I haven't seen any dosage that's toxic. The best collection of safety studies I know of is in the Files section of the vitamin k yahoo group. The highest dosage I saw there, used long-term, was 15 drops 3x/day (so 45 drops/day). They were working to reverse osteoporosis, and it looked like it worked fairly well.
That said, I think most people, if they're just using it for general nutritional support, can get by with a whole lot less. How much? I'm not really sure, I just have DH taking 1 drop/day with his CLO. I've read we can store about a month's worth, there are so many contradictory things about K2 in terms of it being fat-soluble but not building up like A & D that it's a bit odd. I don't understand as much as I'd like.
DS and I have a weird thing, at this point I can't tell if it's because of the A & D in the CLO (my original assumption) or the EPA (a newer idea, which may be a better guess), which is a blood thinner all by itself--haven't read exactly what it does to thin the blood.
I get things like sensitive teeth and bruising on my shins if I go up in CLO too far without enough K2. For 10,000 IU A and 1,000 IU D (and whatever EPA is in 1 tsp of HVCLO), I was taking 10mg of K2. I'm using Carlson's 5mg K2 capsules, it's more cost effective at higher doses. I've noticed the sensitive teeth also with forgetting my D supp and when I skip my mineral supp (my biggest calcium source). So all that stuff seems to work together, but I've actually decided that since I'm so sensitive to the CLO right now, I decided to stop for several months and let my D build up and hopefully get a bit more caught up on minerals (it seems odd that I'm so sensitive to that).
I'm giving DS 7 drops (2-2-3 throughout the day) along with his 1 tsp of HVCLO. He's been stable there for quite a while, no nosebleeds. It took a while for his tartar to start when we were low in K2 for a long time, but it stopped accumulating pretty quickly once I started the K2, definitely noticeable within a month (that it wasn't spreading). But it hasn't really gone away--maybe a little, but it's still noticeable. I'm not sure if tartar can go away except by scraping it off (which, bad me, I haven't taken the kids to a dentist in too long).