To free the ram, you need soft but heavy blows. Cast iron is brittle. Hammering on cast iron breaks it. I had the same problem with both of my Millrites when I got them -- locked up solid. First, mark the column and turret with a Sharpie so you can see any movement and then squirt some good penetrating oil in there everywhere you can. Let the penetrant soak in. Find something like a 4 foot long 6x6 (what I used.) Hang it from the rafters in line with the ram on two ropes. Loosen the nuts and give the ram a few solid hits from the ram from both ends with the end grain of the post. Don't overdo it, and do not be impatient. Squirt some more penetrant on it and walk away for at least a couple hours. Lather, rinse, repeat until you see a bit of movement at your marks. The war is over, now it is just a matter of time until victory. It will pretty rapidly start moving better with each cycle. Keep wiping off whatever gunk gets exposed by the movement, and keep on with the penetrant. I like Kroil for this. After you can push the ram by hand fairly easily from each end to the other, and you have all the corrosion worked out of the slides, start working way oil in. When it is well oiled throughout and no more gunk is coming out, you are done. Swear a solemn oath to yourself that you will move and oil the ram at least twice a year, even if you don't need to.
Edit: Your mill looks really nice, and you have done a nice job on the VFD installation. Perhaps it has been sitting for years and needs some use to loosen up a bit...
