Hey Andrew,Good news, when it comes to SD IRAs the world is kind of your oyster.

No or limited tax benefits unless its in an IRA.

It sounds like you have everything set up for saving, investing, hopefully 401k, IRA's, etc. 

the first holds IRA money and is self-directed, and currently owns four properties that were purchased with cash.  

I knew if I could figure it out and buy a place, I'd have a lower mortgage than my rent and be in a bigger/nicer place.I felt guilty about it, but I did end up borrowing $5k from my IRA (and then replacing what I borrowed).

You can take out as many IRAs and brokerage accounts as you want.

Other than that, request current savings/IRA statements showing significant holdings; most recent tax return, as long as it was prepared by a verifiable third party.

Consider traditional IRA, health savings accounts, SEP IRA, SIMPLE IRA and 401k to lower tax liability if you are not using some of them now. 

Yes, definitely max out your employer match for 401k and max out your Roth IRA.

I have a 401k at work and individual IRAs that are 100% invested in Index funds (the entire US market).