Let's take the questions one by one.
1) If I understood you correctly you only have a portion of your sales reported on 1099-K and no other reporting form. If this is true, you can list the balance of the income as cash.
2) Yes, omit the home office.
3) Yes, TurboTax will recapture the depreciation. Note that you gave it away as opposed to selling it.
4) According to tax law, you must take all your expenses that you are entitled to. This is because EIC is based on income. Do the best you can to reconstruct your costs.
5) Yes, shipping should be miscellaneous.
