Depending on how it is done and what guarantees the government offers and requires of the released entities, interest rates could move slightly higher.

Most individuals can originate the debt these projects require as well so its not as if your signature is opening the doors to properties these partners couldn't purchase on their own either.  

Most professionals will recommend a separate LLC for every $1 million in assets but I don't think that's necessary.

I recommend you hire an attorney for this until you know the process well enough to do it alone.

I'm being required to pay another application fee and then $600 application fee to hopefully get this approved by the Board to allow me to continue running the STR that they approved 6+ months ago. 

I highly recommend them! 

One thing to consider since you are a California resident investing is the compliance requirements for LLCs incorporated in California or operating as a foreign entity here - the rules here are different than most states.  

Further down the line we will also need a CPA to help us with our tax reporting requirements here in Portugal, so again any recommendations I would love to hear them please!

They were thinking of planning another one that required massive loans (7 figures). 

Credit is a factor as bad credit may limit options, or may have the lender require you to put 10 or 20 years of taxes and insurance into escrow.