sad > grievous; heavy; sad doubtful agony > fearful mental anguish
2 Fiercely he flew upon that wicked fiend, 3 And with huge strokes, and cruel battery
battery > battering; assault with many blows
4 Him forced to leave his prey, to attend
leave his prey > (Apparently contradicting 307.30:9) attend > turn his energies
5 Himself from deadly danger to defend: 6 Full many wounds in his corrupted flesh
Full > Exceedingly
7 He did engrave, and mickle blood did spend,
engrave > cut, carve mickle > much
8 Yet might not do him die, but ay more fresh