Form & Workflow design for Approval

Hello DW team,

I’ve set up a Web Form for submitting a payment request approval within our enterprise but encountered a few challenges that I need assistance with: 

1. Round Up, Round Off, or Truncate Decimal within Workflow:
We require the applicant to select whether to round up, round off, or truncate decimals, as our currency does not allow decimals.

Is it possible to configure this option within the Form or Workflow design when specific criteria are met?
If yes, could you guide me on what should be written in the Arithmetic Expression, or is there another specific method to achieve this?
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2. Using Image Stamps for Approval:
Our requirement is to enable approvers to use Image Stamps (one of the configurations under Collaboration) for approving payments, bypassing the need to stamp the document, save annotations, and then approve through the task dialog. Is there a way to make clicking the Image Stamp equivalent to approving the payment?

While I am aware of the Task-General-Stamp option, we prefer to use Image Stamps instead of the Simple Signature available in Workflow tasks. Can this be configured?
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3. Return for Correction Functionality:
Our workflow includes multiple approvers, and we need an additional option beyond Approved and Rejected: a Return for Correction feature. When the 3rd approver rejects a request, it should return to the applicant to edit/attach/correct documents or data entries. Upon re-submission, the workflow should resume with the 3rd approver, bypassing the 1st and 2nd approvers.

Is this possible within Workflow Designer? How can we design the workflow to allow revisions post-rejection, given that typically, approvals block revisions?
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Your guidance are highly appreciated, thank you so much!! 

4. Assigning multiple document numbers into a Keyword Field seperately:

We need applicants to input multiple reference document numbers in the Web Form, which should be assigned to the Keyword Field for establishing Document Relations. While a Single Line Text Field successfully pushes data into the keyword field, when multiple document numbers are entered, they are treated as a single string instead of being separated into distinct entries. I have tried using spaces, commas, and semicolons as delimiters, but the result still consolidates all document numbers into one string.

Is there a specific delimiter that can be used to separate multiple document numbers so they are correctly assigned to the keyword field? Alternatively, is there a configuration or a setting in the Workflow or Keyword Field design to enable this behavior?