Is it better to have a higher value house on lower value land or vice versa?

Your wording is confused, land is property, most commonly people talk about improvement or building value to distinguish from land value, but all of it together is your property value.

1. Am I calculating these right? Who made this assessment?

Looks right to me, (2,453/0.01399)/400,000 = 43.8%. In most states it's county level tax assessors that determine land value for property tax purposes.

2. Outside of payment towards taxes, what does this ratio mean for me? Would it be better to be 5/95 land/property? 95/5? Why?

One thing is that your homeowners insurance would be higher if the improvements were a higher percentage of the property value, since that would cover repairing/rebuilding them, so tax and insurance would offset each other to some extent at each end of the spectrum (of course property tax rate could be increased to offset this in any case).

The ratio is not something I've ever paid much attention to in evaluating properties, and in isolation tells you very little outside of property tax (and not all areas base tax on land value). It could have some value when comparing to other houses in the area. If you build a very expensive house on cheap land and hit that 5:95 land to building ratio while your neighbors are all near 50:50 then you'll likely see your value decline and have a hard time selling. In general, I'd say outside of property taxes it's pretty much an irrelevant ratio.