You want to know if deleting values in a pick list on a Marketo form will delete those same values in SFDC.
No, deleting values in a pick list in a form will not delete those values in SFDC. The fields values you see on your form are a one way sync. You can, however, add values in SFDC and those values will be synced down to the custom field in Marketo, making them available as choices in your pick list.
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