6. misdoubting his intent 'fearing that he had taken on too much.'
12. project plan.
success outcome (good or bad).
13 - 14. wide field...blind Cp. PL vii 17 -20 where M. likens himself to Bellerophon wandering 'on th'Aleian field,' having been thrown from Pegasus (a symbol of poetic daring).
35. horror including 'awe or reverent fear' (OED 4).
49. bushy-points A 'point' was 'a tagged lace or cord, of twisted yarn, silk, or leather, for attaching the hose to the doublet. ' (OED sb1 B5) Points were 'bushy' when tied in tassels. Marvell therefore likens rhyme to a vain fashion. Points were also a byword for 'something of small value' (OED).
54. Number, weight, and measure Cp Wisdom 11:20: 'thou hast ordered all things in measure, and number, and weight.' Cp. also M.'s defence of blank verse in his note on "The Verse": 'true musical delight...consists only in apt numbers, fit quantity of syllables, and the sense variously drawn out from one verse into another.'
(Selected from notes to On Paradise Lost by Andrew Marvell, published as a preface to the 1674 second edition of Paradise Lost. Notes from the Penguin Edition of Paradise Lost edited by John Leonard.)