Have you seen a Rheumatologist? They are your best bet for diagnosing spondyloarthropathy early. Your symptoms along with being HLA-B27 positive should be enough to get you an appointment.
Several. HLA-B27 is an indicator, but you can't diagnose definitively without seeing joint deterioration on X-Ray or MRI. Typically for Ankylosing Spondylitis it's the SI joint that has the most damage, which for me is fine so far. The problems I have are more peripheral joints, and the only changes I have on X-Ray are bone spurs at the insertion point of several tendons which can result from overuse so it's hard to attribute to a rheumatological condition with any certainty.
Most recently a rheumatological told me some people are just "bone formers" which might be true, but is still frustrating to hear as it kind of came across as very hand-wavy.
Second that. There's also ultrasound measurements to help diagnose inflammation related damage. Perhaps a sympathetic rheumatologist might put you on a trial run of one of the moderate RA treatments to see how you do.
