Just a suggestion - see what your LFS
uses to test the water - of the 2 near me, one uses test strips (notoriously inaccurate) and the other uses the same API Master kit I use at home. Hardly worth the cost of gas to get the same or less accurate info than you already have at home. If you use Ammo-lock or anything else to "lock up" the ammonia during a spike your water could be fine but the API test will still read high - Seachem has a test that will show only the free ammonia (toxic).
With regards to your "fish-less" cycle, it took my 75gal 4-5 weeks to be 100% reliably cycled (It felt like FOREVER but still way faster and more humane than using fish). It sped right up when I stopped doing weekly water changes - I just did a bigger water change at the end to bring my nitrates down.