Any chance StdDev around the mean, IMO, is the return, not the price?
and you will assume short term stock return has a 0 of mean so you can compare across them.
I think this strategy might works better in low vol environment. So you are taking the advantage of VIX reverting upward to historical mean as well as buying low IV on the VXX put wing.
Only downside seems to be that XSP is not as liquid as SPX/SPXW options, you will get pretty wide bid/ask. IMHO SPY Options might be a better choice for individual/small accounts.