That's really disappointing your psychiatrist has advised against the study. I've been following this experiment for quite some time and I think it shows potential.
As for how much to take, it really depends on quality, I would probably go by what DeathDomokun suggested and try .15 - .2mg/kg to begin with. .5mg/kg is 35mg for a 70kg person - I would say I probably always use around that, a third of a point, to begin with and test out the stuff, but I have had some decent experiences on that, and starting lower is probably advisable. As doses in the trial are subthreshold anyway the recreational dose isn't what you should be going for if you're wanting to recreate this experiment at home. I'm not sure whether or not higher doses are indicated for depression in the same extent, but it seems like you'd prob be as well trying to recreate the study as much as possible at this point, given that's what (I assume) the researchers have decided will be the most effective.
Not that I advise against higher doses of k for fun. Ketamine is am amazing, awesome drug. I've always felt so much fresher and peaceful after a dose of ketamine, like the 'reset' button has been pushed on my brain. I tend to get quite anxious on psychedelic drugs and even tend towards it on other dissociatives like mxe or dxm, but ketamine is the one that has always felt the most 'friendly' and calming to me, I've never been anxious on it.
I've got good scales and am planning to keep the dose nice and low the first time,just so I don't stuff anything up,and also to see how it affects me.At a .5mg/kg dose it seems like a lot to snort anyway,and it's been awhile,so gotta get my nostrils used to it! 
