But, I will lower my monthly obligation to around $3000-3500 ($2500 new mortgage plus $500 delta on previous home mortgage). 

Can you count on mortgage rates being low enough to refi and make sense for you?

Foe investors who like to purchase land, is every lender requiring it to be financed on a 15 year mortgage instead of a 30 year?

This would be HOA fees, mortgages, utilities, repairs AND your property management fee. 

If your exit strategy is to rent the units then you will want a DSCR loan (30 year mortgage for rental property)  to refinance the fix and flip loan.

Exploring creative financing options like portfolio loans leveraging combined property income, hard money loans based on property equity, private money lending from investors, or negotiating seller financing for new property acquisitions could offer viable alternatives to support your investment goals.

I can get 30y just under 8% currently from my local bank (7,300/mo mortgage for $1 mil). 

Is your DSCR ratio greater than 1-meaning are you cash flowing (according to the lender's criteria of mortgage, property taxes and insurance (and HOA) if applicable).

Also worth noting that he took out a reverse mortgage on the home before he passed away.

By this I mean I was renting it out in 2021, but depriciation and mortgage made it income negative.