I was thinking about an strategy of doing Cash Out Refinicing putting that money in the stock market (distributed in ETF and some "safer" stocks) to get around a 6% anual return (estimating that low because is the "standard" average, however my current stock portafolio has a cummulative return of 66% in the last 4 years).

It can generate better returns, or at least more predictable returns than other asset classes like stocks, bonds, crypto, and other alternatives. 

I give a $20 gift card to the local grocery store day of move-in so tenants can stock up on a few staples or pick up something ready-to-eat from the deli.I have given wine, but you need to be careful & not assume everybody would welcome such a gift.

Partially because you did not rent it for an entire year but mostly because of upfront expenses: getting it ready for rent, buying furniture, electronics, and other furnishings, stocking up on initial supplies, and so on.

What should be my stock vs real estate vs fixed income ratio?

but some parts of the country there is lots of old stock that can be recycled.I mean you could go into Gary indiana right now and buy 100 homes straight away.. 

Not always easy to get unless you stock a couple of cords, which takes a lot of space.Propane is going to be your friend up there.

I would hazard a guess that 90% of all investors that ever made any serious money in real estate did it the old fashioned way - they bought the property and held the property, the same way that 90% of all investors that ever made any serious money in the stock market did.

Are we going to see returns that look like stock market numbers for the foreseeable future. 

Take a free an clear property, pull half of the equity out (tax free) and invest that for example in the stock market.5k-10k in monthly income after everything sounds like 20-30 units.