1. Legally are we expected to pay franchise tax for Delaware? If so how is it calculated?
Yes, you must pay the DE Franchise Tax. It's calculated on your Assets and Shares issued as of 12/31/XX. Weird, I know! For CCorps, its usually $400-$5000+, and note that your bill will be higher if you have more Assets at year end.
2. Practically should we pay it now or hold off until we know we have a viable business?
Pay it now; even if the business doesn't work out, you'll still be expected to pay.
3. What are the consequences for missing the March deadline (which we did)?
Penalties are about ~25% of the tax due, plus interest. So if you If you were supposed to owe $400 back in March and then pay late in September, expect a $530 bill. If dont pay for 2 years your corporate charter will likely be revoked.
4. Since we already missed the March deadline, what might be the consequences if we do not pay at all (this year)?
See above.... and hope this helps!