A freewheel tool is similar to a cassette lockring tool but has less 'pronounced' splines and is longer.
We stick that in a vice at work and just unscrew using the wheel but you only really need a spanner for the tool and a good arm to hold the wheel, no chain whip.
Not sure about ratios, may want to go to a bigger ring up front or smaller cog up back as i may be right in think you will pedal out faster on the larger wheels?
No idea about chain line though! Think you would have to have a play up front as the ss freewheel cant move like on a freehub body.
you can use up to about 1.5mm of spacers behind any freewheel
or to get the freewheel to 'move' even more you can reposition the spacers on the axle ('til you get the right chainline) then re-dish the rim to suit. FAFF, but you may end up with a non-dished and therefore theoretically stronger wheel