If the home was listed with FHA/VA financing accepted, the owner/investor should be adequately experienced to anticipate the scenario you describe. RELAX.
If however, the home was not listed with FHA/VA financing accepted, you have imposed thousands of additional dollars of cost on the seller in addition to a gamed appraisal.
If it were my listing, which would have appeared 'AS-IS' cash or conventional, you will need to pay in cash the difference in negotiated price and appraised value. I will have six buyers waiting for you to stumble or cause negotiations to be reopened.
There is much we do not know regarding your situation. However, experience suggests you can RELAX. Investors like to see happy folks moving into a home they just rehabilitated. Many are noble folks looking to match beautiful homes with deserving home seekers.
I would relax, enjoy your holiday and see what happens.
Today more than ever, listing agents need to take great care when assigning "asking prices" to property because as you are finding, if financed, they must appraise to avoid complications.
No point in worrying until the numbers come in.....I like your chances!
Appraisals have become more of an issue as prices are increasing. It's ironic - in a declining market appraisals are easy since past sales prices were higher. So even though your property may be worth less in the coming months appraisals were easy. Now as the market is improving appraisals are more challenging.