My husband is in medical school and I just finished my masters in engineering.

This means it must be designed and built with specific engineering requirements and most of those seawalls are not.You are on the right track with figuring out the BFE and elevation of your ground level.

It's a great way to burn through whatever money you have, while dodging state regulators. 

burning outworking in the business vs on the business

Historically, most investors use a 10% vacancy rate AND a 10% maintenance rate, to avoid getting burned when markets change.Those rates change based upon the Class of the property.

O3 is highly reactive and binds with one of the O's to anything organic, basically burning up (oxidizing) anything organic and going from O3 to O2. 

An engineer recommended us to dig out two feet of the entire section and fill it with topsoil.

Ground up construction takes longer to complete and you need an experienced team to help you accomplish you goals - You also need to address soft cost first - survey, engineering report, architectural drawings, demolition permit (asbestos report, pest control report) etc, before you go for the hard cost Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

But I have thought a crash was coming for a while and the financial engineers keep make asset prices go up so who knows.

You will burn out if you have 0 fun in life, not taking it to the extremes and not spending more than your income justifies is the key, that and budgeting for it properly.Did I mention using credit card offers as toilet paper?