An S corporation does not actually pay dividends as does a C corporation, so an S corporation would not issue a 1099-DIV unless it were liquidating. Distributions would be reported on your K-1 (1120-S).
From the first line in your question, if your ordinary income (as shown on Line 1 of your K-1) is $50,000 and your Section 179 deduction is $15,000 (as shown on Line 11 of your K-1), then, barring any further relevant figures and only taking those two figures into account, your basis at the end of the year would be $50,000 ($15,000 beginning of the year basis PLUS $50,000 ordinary income on Line 1 LESS $15,000 Section 179 deduction).
