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.