"Do the 1099 forms show the total amount sent or just the taxable amount?" - The 1099s SHOULD show only the fee + bonus. In the past I have had some MSPs that the 1099 reported everything to IRS--fee, bonus, reimbursement. I even had one MSP include the fees they paid to Paypal to send me my payment as a 1099 expense to me.
Rarely does even a properly prepared 1099 accurately align with your meticulous records because of pay dates. They will reflect prior year work paid for in the current year and current year work paid before 12/31. Don't worry about it. Lets say you have 3 1099s. List them on your return. They total to $X. Your records show $Y as total fees plus bonuses with your supporting documentation. Subtract $X from $Y and consider that your total taxable receipts and enter that as your non-1099 income. You now have accounted for every penny of income between the 1099s and the self statement.
The code really is almost irrelevant. Years ago I used 541910 and have never been asked about it since. I'm not sure if that code even exists anymore.
Most of the categories on the Schedule C do not apply to shoppers. Advertising? Commissions & fees? (we can't subcontract to be paying someone these), etc. If you take your computer for repairs you might have a 'repairs and maintenance' item, but expenses of using your car are specified elsewhere. There is, however, a Miscellaneous expenses area and this is a useful catchall. My personal preference is to claim every cent I get from the companies and then create a line item called "Reimbursed business expenses included in income" in the expenses section of the Schedule C where I subtract out all reimbursements. I do this for two reasons: First it makes the income line of the return more feasible as being a job rather than a hobby. Second, my statement of "Reimbursed business expenses . . ." pulls out all those reimbursements and makes a following line item I create called "Unreimbursed business expenses" more feasible and logical, I believe. Whenever you do a flat fee job and are required to make a purchase, that purchase becomes an unreimbursed business expense. Similarly, if you are being reimbursed 'up to $1' and walk in the store to find that the cheapest item you can reasonably locate is $5, you must spend $4 more than you are being reimbursed to be able to get the job done. I claim the $4 as an Unreimbursed business expense. You do a job where you are required to purchase a regular burger, small fries and small soda and are reimbursed 'up to' $4 and the price for those items comes out to $4.93, you have an unreimbursed business expense of 93 cents.