If it's something you're going to wear long-term, why not get it up to +2? Its previous blues don't seem incredible (+1 str and +10hp), so even
if you lose them, it won't be a huge drop. Get lots of lucky powder and play it safe.
As for the SOM, with 5x lucky, why not? Always buy the extra powders, stones, etc., however, to increase your chances of success.
Y.
P.S. I will echo Masta's comments about your in-game richness
