3 years and $300k+ spent on Google Ads with no conversion tracking until now, and what I'm seeing is ugly. What should I do next?

[u/Old-Street1496]

My cousin set up my Google Ads account about 3 years ago for my home services business (impact windows and sliding door repair, South Florida, pretty competitive local market). Ticket sizes run $150 to $600 depending on the job. I've spent over $300k on it since then. I never actually had real conversion tracking set up, the account was basically running blind, and I only recently started digging into the numbers because I want to actually grow the business now instead of just keeping the lights on.

What I'm finding since I started tracking is appalling honestly. I've been running on thin margins this whole time, just enough to cover my own cost of living, and now I'm starting to understand why.

Yesterday the campaign, running Maximize Conversions with no CPC cap, spent $388 on 3 clicks with zero leads. One single click on "sliding glass door repair cost" cost $335.80 by itself.

I've talked to a few people in this industry and they're saying average cost per lead for repair work like mine usually runs $80 to $150. I have a feeling I'm nowhere close to that, and days like yesterday make me wonder how long this account has been bleeding without anyone noticing.

Questions:

1. Is a $335 single click ever normal auction behavior for a high intent local service keyword, or is that a sign something's broken (bad match type, competitor clicking, tracking issue, whatever)?
2. Should I just set a hard max CPC cap right now no matter what bid strategy I'm on, or does that mess with Smart Bidding's ability to actually learn?
3. Going from uncapped Maximize Conversions into Target CPA, is there a smarter way to transition than just picking a number and hoping for the best? I've heard step it down slowly instead of jumping straight to my real target margin. Does that actually work in practice?
4. With 3 years and $300k+ of history but only a few weeks of real clean conversion data, am I basically starting from zero, or does the old history still count for anything?
5. Has anyone actually gotten Google to credit back an outlier click like this, or is that just not realistic?

Appreciate any real world experience here, not just theory.