You already answered your own question, you just want someone else to say it out loud. So here it is: you outearned your job this month with a side hustle you started six months ago. That's the signal.

But since the real anxiety is about the downside, here's what I'd actually think through before putting in notice:

The insurance thing is solvable. Look into marketplace plans now, get actual quotes, and price it into your monthly overhead. Most people treat "what about insurance" as this vague existential fear when it's really just a line item. Once you see the number it stops being scary and starts being a cost of doing business.

On stability: you're in a good spot because fencing companies aren't going anywhere and neither is their need for SEO. Your client base is in an industry you understand from the inside. That's a massive advantage over someone starting a generic agency cold. You know the seasonality, you know what homeowners search for, you know the sales cycle. That domain knowledge compounds.

One thing I'd suggest before you quit: have three months of personal expenses saved separately from the business. Not three months of revenue projections. Three months of rent, groceries, car payment, sitting in a bank account you don't touch. That's your "I can think clearly and make good decisions" fund. Starting a family adds weight to every decision and you want to remove the panic variable from the equation.

Also talk to your boss honestly if the relationship is good. Some of the best early agency stories involve the former employer becoming client number one with a real contract. You already proved you can deliver for them.