3. Registering as a company makes no difference since I won't have any taxable sales I can write it off against.
Sales, no.
However since you are mining for profit - and business profits are taxed - that is where write offs come in. In the US at least, the miners are Capital Equipment required for the business. In fact the IRS views them the same as any other computer or data server so they are write offs along with any import duties.
I think you're mixing VAT with normal income/profit taxes (I was probably not clear). When importing I have to pay 25% VAT + some small taxes. VAT is not possible to write off unless I have sales with VAT added. E.g, I have to pay $1000 import VAT for two miners. To write it off, I need to have sales to consumers for e.g. 4000 + 25% VAT ($1000).
If it was just normal income tax, I could write it off against the profit tax I have to pay.