Used to swear by the cheap click types myself, figured a torque wrench is just a spring and a lever, how much could Harbor Freight mess that up? Then mine clicked early on a brake caliper bracket and I nearly lost a wheel on the 10. That CDI tip from eBay is the move, I grabbed one for 70 bucks and it's been dead on every time I check it against my buddy's digital. Night and day difference in how solid the clicks feel, too. Phoenix heat probably doesn't help the cheap internals either, so you're not crazy for thinking that played a part.
Man, that hurts to read. Phoenix heat plus a warped head is a brutal combo, I feel for you. Same thing almost happened to me on a Subaru EJ25, that HF click is just a suggestion. What saved me was biting the bullet on a used CDI torque wrench from eBay, paid like 80 bucks for a nice Snap-on industrial model.