1) Do you possibly have medical receipts you can submit to allow you to tap your HSA penalty-free as needed?
2) What taxable income did you use when calculating your ACA premium? Your MAGI might be lower than you think since you will be selling from your taxable account to create income up until age 59.5. That depends on how large your capital gains will be. If your MAGI will be lower than you think, and therefore your ACA premium is lower than expected, your overall budget could be lower, allowing you more wiggle room.
3) Is there part-time work you might be interested in doing that could allow you to semi-fire and be able to take fewer withdrawals until you reach 59.5, if necessary?