I think you are on the right track now. I have split wood for many years and without seeing your design, I simply can't imagine a 140 handling the job when you consider all the torgue and pressures involved.
If you find an AC only buzz box 6011 or AC rated 7018 would be a far better choice. I welded many a farm equipment with an old buzz box.
Having said that, small wire welders for sure have their place and I bet you'll find many uses for it. Check around, many used buzz boxes setting in the corner of garages collecting dust. You will probably have more applications for it anyway, especially if you have to weld outside on windy days or rusty metal.