I am looking to create a legitimate business, that would pay us a salary and also allow us to continue to make retirement contributions.

Once you agree on things like roles and financial contributions you definitely need to have an attorney draw up the documents to make sure you are all protected and any negative outcomes are contemplated in advance. 

It sounds like you're in a place where contributing capital is much easier than committing time.

But the current outlook is for more and more taxes to support more and more giveaways to people that are not contributing their "Fair Share" to support the economy.

I don't contribute to it so it just kinda sits there.

At least in real estate, usually there is a lender sanity checking your ability to not lose your shirt and you get to contribute to the decision making (for good or bad).

My first approach was to increase capital contribution of the original investors by 20% in the cap table, but this is wrong and causes issues with taxes and later disbursements. 

Maybe partner up with a trust worthy person to find deals for them and put in sweat equity as your contribution.

Same for your question.SDIRA has strict limitations on how much you can contribute per year, but the funds can come from anywhere.

Half of my contributions go to VOO and half to standard TRs.