Do you realize that you are working with the impeller section of the turbo assy?

Most of these units are designed to go no faster than 80,000 rpm(80k).

"The first picture is of the turbine blade, a modified compressor wheel from an old auto turbocharger.
"

That is essentally correct, but why, are you trying to drive a compressor blading assy, with steam?

 If I were you, I would abandon this section of the turbo, and install- 4 1/2inch nozzels, tangentally at 90* to 180* vertical of the actual turbine half(exhaust housing) of the turbo. Although this does not account for the compress-ability of air, I feel you could do quite well with such an arrangement, using High flow volume rates of steam. Also you must get the oil-bearing up and running with some sort of oil-pump to the centre bearing. Its probably best to sparge the original air(combustion product gass inlet) with the output from the impeller section. In this way you could sparge aire into the cast-iron housing (stainless steel) with each of the 4    1/2in steam inlet nozzels. Have you noticed the vaning of the exhaust turbine?

 You could safely gear down the shaft(@80k) to a system of high-speed belts to drive an alternator at 3000rpm. But balence issues would surly arise, on your pto-shaft. Unless your planing to use volume flow to drive another 'reaction' turbine set, which I feel is not the case based on your comments. By the way which element of the turbine shaft are you going to convert to the pto? be vary carefull when contemplating the 'open' end of the shaft. (pto, power take off)