Valuation / seller financing precedents

What are the most reputable sources I can show a seller that outline typical valuation multiples and the percentage of a deal that’s usually seller financed? I know about the Pepperdine reports for multiples and IBISWorld for industry info, but I expect some skepticism around those numbers during negotiations. In larger deals, there’s plenty of data on deal structures and multiples, but I’m not finding much that’s reliable for lower middle market deals (e.g., $2M-10M EV). Any suggestions for reports or databases that are respected for this size range? For context, I often see sellers benchmarking deals on a single comp that’s five times bigger than theirs, mixing up EBITDA and SDE, and adding back every possible expense. When I make an offer grounded in reality, I’d like to show them data that helps them see it as a fair price.