I reviewed all your points and here is what I did:

Fixed:

Proposal Unvote — Vote state now persists when revisiting the page. You can unvote correctly.

Witness icons — Updated as you suggested: ✅ = voted, ⭕ = not voted.
Kept as is:

Delegation (0.000) — Entering 0 without decimals is the correct way to revoke. The placeholder shows 0.000 as a format hint, but the input 0 is what the blockchain expects. This is standard Steem behavior.
New APK with all fixes: https://drive.google.com/file/d/1xCqrBtHbT9AgQrP582Bd0RqkTX9e1skA/view?usp=drive_link