1) BTC premium typically reduces over time as BTCUSD rises, but at the same time the numerismatic value of the coin also improves with age as it becomes rarer to find one for sale or viewing.

2) safety deposit box or other thoroughly-secured location. Viewing of a loaded coin by others is not recommended, or at least should consider the risk that the viewer may try to steal from you.

3) The effect of grading is unclear, as the digital value of the coin conducts such premiums. If you cannot grade within your home country, its likely not worth it. High-resolution photographs are probably as valuable as a graded slab, as it allows the buyer to evaluate the condition.

4) shipping out of country is tough, as it carries a risk of loss and can be difficult to correctly insure the coin. (notwithstanding the shipping logistics, an escrow such as minerjones is highly advisable). A local buyer is probably your best bet, even if its a lower bid than a US buyer.