You mention in your questions a schedule C. Please be clear that as an S-Corporation, a schedule C can not be filed. This is for Single Member LLCs who are disregarded from their owners, or for sole proprietors only.
You asked, Can I combine the 1099 and K-1 income on my Schedule C as income so that my business expenses and be applied to both sets of income?
If you have an SCorp, you are required to file form 1120-S, not Schedule C.
Please be aware that for S-Corps, there are "reasonable compensation" clauses imposed by the IRS. Please pay close attention to these because you could lose your S-corp designation. Please see this IRS link for more information.
In answer to your question, yes, you can get months rent checks for the approximate cost of the home office, and other office expenses can be reimbursed directly through the expense reimbursement protocol of the business. The truck can't be "reimbursed" or paid for by a car allowance agreed upon by a corporate resolution. It has to be depreciated.
