What is the blower HP needed for a 12ft column of water?
I don't think this is going to work.

Shop-vac posts their specs here:
https://www.shopvac.com/specifications/quiet_series.asp

Even their most powerful vacuum only has a sealed pressure of 64 inches. I would presume that the blower would have the same pressure.

I don't know specifically what you are using an air pump for to close a pool but I think you may need to use a compressor or some other device.

Good luck!