The weight can certainly be a problem. The rating for the PCW5000 winch is the force applied to the load, so it should lift approximately 2200 lb (1000 kg) at its peak capacity. If you are dragging, you are pulling the weight of the log plus you must factor in the friction. For example, a skidder will normally be able to pull approximately its own weight in payload, with logs suspended. But the skidder winch normally has more pulling capacity to overcome friction. And if the log comes against a root or a small stump, the winch will not be able to pull it (wire rope and chokers often break).
The same principle will apply to our winch. If you use a pulley to create some lift while pulling, it will move larger pieces; if you shape the log end to reduce friction or use the skidding cone, it will help too. The length of the log dragging will also affect its winchability.
So it is very difficult for me to say how this would work. One thing I know is that using blocks, you will be able to move them, but not as quickly.