Forgive me if this has been posted, but i have a few questions of powering a 40/50w merc.
Could I use a single lamp preheat ballast (universal 202-B-TC-P .55 line amp) to power it?
Could I use a two lamp f40 RS lamp ballast (advance R2S35-4-TP .67 line amp power factor corrected) but between the red and blue wires, and insulating the yellow, or running two of aforementioned merc types in series?
Could I use a single lamp f40 RS ballast (universal 413-C-TC-P .65 line amp)? Thanks.

The line current tells nothing, you have to find out the lamp current for these ballasts and the lamp output configuration (series, parallel in phase, lead-lag).

If the ballast feeds the full rated 0.43A into the F40 lamp, it may work (at about 35W), so better use the lamp only horizontally (so the liquid mercury would flow out of the coldest spot behind the electrodes to the warmer central tube section)