Yeah I've seen youtube videos who show that setting up FoCal targets can be difficult if you don't have proper lightning. https://www.youtube.com/watch?v=ALDWPtYwZ6I
I would suggest you to do the calibration at night (to avoid lightning variations) and with several desk lamps (preferably incandescent bulbs).
For parallelism you should use a bare mirror (no surrounding plastic frame) laid flat against the target, adjust the tripod head in order to center the image of the lens barrel on the center focus point.
Also for the distance it's advised to use roughly 50 times the focal length, so for a 60mm, you'll need 3000 mm or 3 meters. But that depends on people, some prefer to do the calibration at their shooting distance.
From the values you gave me looks like you need to put something like 10 or 15 in the MFA values (don't remember which sign to use). For me that's abnormal and it could vary a lot depending on the distance you shoot at. If the lens worked flawlessly on your 600D, you should send the camera to Canon (the lens isn't necessary).
Unless you can prove to Canon that the camera has an issue (maybe by measuring the AF coverage, I'm still waiting for my camera so I don't know if it'll work) ; I would wait a few months for the repair centers to get maybe some sort of notice on how to fix the issue and on what to look for. Because up until now, on first try the repair center will only do some software adjust, and you had to send the camera a second time and even a third time to get it fixed. But it now looks like some people are seeing their camera either replaced or repaired (might depend on where you live) and apparently one repair center is getting at least twenty 70D per week (https://www.flickr.com …/72157639283256254/page2/). So maybe you wont have to wait too long.
Last thing : having great LiveView focus doesn't rule out a lens issue, because a lens could also need some MFA to perform well. The only way to rule out a lens issue would be to test it on several bodies, like you did with your 600D, so I think that in your case we can rule out a lens issue.
Thanks, strange thing is though that I just tried it again using area focus on every section starting with the middle and several single focus point mostly in a cross across the middle and up/down middle and got exactly the same results.
I also used MFA blindly to backfocus 10 and 20 and got the same results i.e. front focussing by the same amount. Nothing changed.
I am now lost, think I'll just get a refund and check out my options later. I can't justify going through all that effort to resolve what is so obviously a faulty piece of equipment. If it cost a tenner, I would bin it but not £850.
Thanks for your help anyway.