due > appropriate, fitting
3 And love to dislodge out of its nest: 4 Still when her excellencies he did view,
Still > Ever excellencies > {Surpassing merits}
5 Her sovereign bounty, and celestial hue,
bounty > virtue, goodness hue > appearance
6 The same to love he strongly was constrained:
The same > [Those qualities]
7 But when his mean estate he did review,
mean > lowly estate > rank, status; condition
8 He from such hardy boldness was restrained, 9 And of his luckless lot and cruel love thus plained: