We don't have synonyms for blessedly yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are blessed, pleasedly and obsessedly.
"1599 Therefore should every soldier in the wars do as every sick man in his bed, wash every mote out of his conscience; and dying so, death is to him advantage; or not dying, the time was blessedly lost wherein such preparation was gained"
"1599 Therefore should every soldier in the wars do as every sick man in his bed, wash every mote out of his conscience; and dying so, death is to him advantage; or not dying, the time was blessedly lost wherein such preparation was gained"