Should a solo founder run paid ads?

Short answer

Not until organic conversion is proven. Paid traffic amplifies whatever your page already does — if 100 free visitors produce no signups, 1,000 paid ones will produce no signups and an invoice. Ads are a scaling tool for a funnel that already works, not a discovery tool for one that doesn't. The exception is spending a small fixed sum purely to buy traffic quickly for a conversion test.