This is the proper arrangement. Editors usually omit the first 'most good,' to get their favourite decasyllabic verse, heedless of the loss of force.
"Think you I can a resolution fetch
From flowery tenderness?"
It appears to me that a negative is required to make the passage more correct and natural; and we know how frequently it is omitted in these plays. Here, however, I think, 'a' has been printed in its place (see on Twelfth Night, ii. 2), for the compositor probably did not pronounce the t in 'cannot,' and so made it 'can a.' I therefore read, 'I cannot resolution fetch.' Heath takes 'Think you' as imperative, not interrogative, like Bethink you.
"Thou art too noble to preserve a life
In base appliances."
It might seem better to read By than 'In'; but it is not safe to meddle with prepositions. See on iv. 4.