My husband and I have recently purchased our first home and investment property using an FHA backed loan with a 203k rehabilitation loan component.  

So, my question is, when does anyone here think the appropriate time to go all-in is?

I would post it here, but every time I answer someone's question and point them to the appropriate resource I get flagged somehow by BP for self promotion even though most the resources I suggest have nothing to do with me, then nobody benefits from hearing about the resource but that's BP's loss I guess.

In hindsight I should have negotiated for a credit before submitting the offer, I don't feel appropriate asking for it now after reading some of the responses on here.

Tell them you want them to find an appropriate home for their family but also protect your investment.

They could be willing to do an equity share where, depending on the agreed upon amount of time and money invested from both parties, the percentage of the profits are split appropriately once the property sells.  

When the last tenant vacates, if appropriate, the deposit is returned to that person or couple.

Is this an appropriate place to start my offer.

I do not know where you are at on your journey or what is the most appropriate for you at this point. 

You can definitely do it, you just need to make sure you're doing all the math and research appropriately.