I wasn't reading too well yesterday, and I apologize to Nathon for taking what he said out of context.
A regular 3 pt implement (plow or such) does transfer weight to the tractor like I said above. Nearly every log winch I've seen does not, by design mostly, as they're trying to lift the nose of the log, much like driving with a 3 point implement raised in the air.
The problem gets worse when the hitch point gets higher or further back, WD's tong mount is a pretty extreme example of that. It's all about leverage and the further from the pivot (rear axle), the more force that gets applied. I'd feel a lot better using the hooks you have added (that I didn't notice the first time around. Still gonna have to use caution, but it's gonna be a lot less likely to be trouble than towing from the top mount.
Here's a pic from the Farmi operator's manual (available here:
http://www.farmiwinch.com/10-farmi-jl501-skidding-winch-owners-manual.html ) They say to skid only from the chain hooks or the lower pulley, not the top pulley - that's for winching only. I know manuals are uncool, but there's some good info there, even if the translation from Finn? isn't perfect. Notice the lower pulley and chain hooks are almost in line with the lower links (just a little above)
The blade is gonna stop you from going over - UNLESS you're going up a steep hill that lets you over center, or something breaks (that never happens, right?) If that little Japamassey doesn't have a GOOD ROPS on it, I'd strongly suggest adding one, just in case. (Hypocrite alert - my 180 MF doesn't have one, but it's also 7 feet wide and weighs 10,000 lbs with loader and weights, and I generally only skid on snow so I'm traction limited.)
Nathon, you're also right on purpose built log skidders, but the difference is that an ag tractor is generally set up to be heavy on the rear - roughly 35/65 F/R weight split, and a skidder is built pretty much opposite. It takes a lot more to get the nose up.
One last note - to get weight transfer with a 3pt skidder, you'd have to hitch below the lower links. Not practical at all for a small tractor, doable with a large farm tractor, but probably not necessary by the time you get that big.