It’s a larger house (3500 sqft. 5 bed), but is secluded, private, centrally located, and sits on nearly 3.3 acres of the East Bay Hills, with open space as far as the eye can see outside.

Hello,I'm looking for advice on my offer strategy for a house on the market I want to purchase.

If it's the case that you are in an area where this is a consistent problem, it may be better to install a whole house surge protector at the main panel.

You can allocate those proceeds any way you want - as equal down payments or buy one for cash and others with loans - It doesn't matter a bit as long as you use all of the cash and purchase at least as much as you sell. 

I've helped people with SBA loans to purchase real estate for a business, but for buying rental real estate, the DSCR loan is a much better option.

Here’s how I’m currently thinking about it:The interest rate on my existing property is 3.5%, so I’d like to maintain that rate rather than refinancing the entire loan.

There's no workaround for bringing it in house.

If you Bank/Lender does not allow it you can refinace the mortgage into a DSCR or true Portfolio loan program. 

You've probably heard of big Landlords losing property, but only because they were flagrantly violating Fair Housing, running a slum, or otherwise violating the law in an egregious manner.

House Hacking is a good route to get started.