OK look, asking a coach what he can lift is immaterial in my view. I know some great lifters who are terrible coaches, some terrible lifters who are great coaches, and everything in-between. For the record I'm not particularly strong. I can pull about 2x bodyweight, but that's nothing to write home about either
I'd also look at things like farmer's walks. I wouldn't pull more than twice in a 7 day cycle
I've never tested myself, I'm not interested in endurance. Also, it's immaterial as I commented on earlier. But to satisfy your curiosity, I can probably do one set of 15 or so at the moment.
It takes a lot of strength, and some technique to boot. I can't do one.
Get someone to steer, my friend! What you're doing isn't particularly safe or effective.