I’ve been hearing about taking the bonus  depreciation and while it sounds like it would be a great strategy if we were full-time real estate professionals the IRS considers our rental business passive.

The big one:  would the IRS consider this tax evasion? 

I would hop on the phone with the guy and share your specific concerns.

It will take a couple years but when the IRS catches up, you may get a letter asking for a few details. 

If you moved because of work, military assignment, work in the intelligence industry, health reasons, or another IRS-approved 'unforeseen circumstance', you may be eligible for a pro-rate exemption.https://www.nolo.com/legal-encyclopedia/the-partia...https://www.irs.gov/publications/p523#en_US_2018_p...

You will have to elect how the IRS should tax it.

From there you'll need to hop on over to the Bigger Pockets Marketplace to take a look at my offerings.

2/ Will I need to follow any special guidelines to be able to show the IRS that the money that I used for the investment property purchase really is the money from HELOC?

I didn't need an ITIN till I submitted my first tax return with the IRS. 

The difference with a DST is that the IRS issued a revenue ruling acknowledging that beneficial interests of a DST are like-kind to real estate for the purposes of a 1031 exchange.