Some stream-of-consciousness thoughts below:
Change 0 to 3 in cell G3
You mention withholding an extra $50/paycheck - do you get a tax refund when you file, or do you owe ~$0 when you file?
Change name in A111 (e.g., add "- repaying to 403b") so there is no SL interest deduction in G15.
If you put all HSA contributions into the employer-sponsored plan, you save the FICA taxes on that amount. Could you put $6750 into that plan, and just not fund the one you do outside of work? Or did you assume that "employer-sponsored" meant "employer contributions"?
If you don't know where $3000 in Miscellaneous, plus ~$12,000 in "after-tax investable" is going, getting a better handle on those expenses should be a high priority.
Putting the full $6750 into your HSAs seems a good target - sometimes it's easier not to spend if the take home pay is lower....
Good luck!