Not touching classic but ur 2nd macro should work. It’s possible your targettarget in testing the 2nd macro was invalid so you could add some additional checks to it.
#showtooltip Blessing of Protection(Rank 1)
/cast [@targettarget,help,nodead] Blessing of Protection(Rank 1)
Personally I’d go with this so you have more functionality but replace the [] with [@none] (forces the hand to display, which you then clear) so it doesn’t auto self cast.
#showtooltip
/cast [mod:alt,@player] [@mouseover,help,nodead] [help] [@targettarget,help,nodead] [@none] Blessing of Protection(Rank 1)
/stopspelltarget