@Wayne Chou, as Greg notes, it would be helpful to see more of your calculations and how you derived them.As for what is reasonable, this can only be determined by you.  

I was able to withhold less from my W-2 income in anticipation of these savings, providing me cash flow in my pocket each time I got my paycheck.It could be beneficial to engage an accountant to help you assess the cash flow and determine if you are maximizing potential cashflow derived from taxes!

Long-term rentals typically derive at least 80% of their gross rental income from residential dwelling units.

Just because the true supply of Bitcoin is very stringently determined (one new Bitcoin mined roughly every ten minutes, no matter how many people are actively mining) does not mean that someone cannot extend the derived supply of Bitcoin through the use of debt (think fractional reserve banking).Crypto is still too volatile to be money. 

I know the Guide isn't law, but in my experience its not the law that is solely enforced, but also the derivative regulations, formal guidance documents, as well as case law history.

Here is some clarification:When property inside of an IRA is financed, it generates UDFI (Unrelated Debt-Financed Income), the income derived from the leveraged portion of the property. 

@Yi Chu,Another important factor you need to understand is that when an IRA is invested in leveraged real estate (most MF deals are), the portion of the income derived from the leveraged portion of the property will be subject to Unrelated Business Income Tax (or UBIT), which can be offset by using depreciation and other deductions.

It’s true that the IRA will incur UDFI/UBIT on the income derived from the same % leveraged.  

Portfolio = Income derived from financial instruments like dividends (including REITs), interest, royalties, and capital gains.Mostly income w/out loss potential, and favorable tax rates.Cap losses may offset cap gains w up to $3,000 loss.

Experience derived from extensive dealings with people for 40 years professionally and in the capacity as a landlord.