doubtful > uncertain, unpredictable
4 Came running fast to greet his victory
greet > congratulate him on (SUFQ)
5 With sober gladness and mild modesty,
mild > gracious
6 And with sweet joyous cheer him thus bespoke:
cheer > expression; bearing bespoke > addressed
7 "Fair branch of noblesse, flower of chivalry,
noblesse > nobility
8 That with your worth the world amazed make, 9 How shall I requite the pains you suffer for my sake?