Well of the 20 or so yrs I've successfully kept fish, I've NEVER encountered so much trouble cycling a tank!
last night, I got home from visiting for Christmas dinner after 1:30am. checked the ammonia levels and found them to be close to .5. Previous day (Christmas Eve), I'd done a partial change, getting down to less than .25.
Since I needed more water conditioner anyway, I went to Big Al's; where I argued with 2 different people who adamant that one should not even consider a water change for at least 6 weeks when cycling a tank for a Betta; regardless of numbers - which need not be tested in that time

. I said,"I'm sorry, but while I agree that Betta's are relatively hardy, no fish can tolerate ammonia levels that are off the charts for a prolonged period of time!" I've had fish for many years, and until now, I've never even seen a major cycle numbers with only one fish in a 5 gal, especially one seeded from an established tank! Then I was told to try the ammonia chips... This would prevent any ammonia. been there, done that!
Then we agreed to try cleaning out everything thoroughly, and soaking everything in vinegar and water. Since I clearly have yet to get past the first day of a cycle, I've nothing to lose. Filter sponge was just rinsed under tap water; not vinegar. I've even thoroughly cleaned his Betta jar (feeding jar). In the process, I dropped and shattered the heater

so off I went to replace that
So this was the perfect opportunity to replace the gravel - which I'd wanted to do for a while anyway. Now every nick and cranny is spotless.
Now he is in the Betta jar, floating in the tank ... Just in case there is any more fine particles from the new gravel; even though it was well strained and rinsed before going in the tank. I feel bad for him there, but he'll survive overnight.
If I were to see ammonia tomorrow - without a fish present, I'd have to conclude that there is a "hardware" problem somewhere!
Fingers and toes crossed!!