sprained ankle ... how to get back to racing asap?

[KnottedYet]

You said they xrayed you twice, and found no broken or cracked bones? Whew! Sounds like one doozy of a sprain!

What are the PT/PTA mobilizing? (why do you need mobs?)

Sounds kind of like something in your hindfoot is still pretty unstable. Do you already have custom orthotics or insoles the PT had you get? If not, and you're willing to spend $35, I'd suggest you get Superfeet Green insoles or some other very firm support insole with a deep heel cup. The deep snug heel cup will help to stabilize the hindfoot (and so also the ankle) and maybe help cut down on inflammation from excess movement.

Cutting down the irritation/inflammation and the excess stress might let the sprain finish healing. Keeping things stable might let the sprained and loosened ligaments tighten up a bit.

Ask your PT to watch you walk barefoot down the hall. Ask them where they see the instability as you weightbear and progress over the boo-boo foot (is it hindfoot or forefoot) and ask if they can recommend an over-the-counter insole to correct the instability. (if it turns out to be a forefoot problem, they'll still want you to have some OTC insoles so they can put wedges on the underside to stabilize the forefoot. But if it's forefoot a deep heel cup won't be so crucial.)

Your best bet is to have an eyewitness check out the behaviour of the foot/ankle while walking. I can throw ideas out there, but I wish I could see it myself! Take everything i say with a grain of salt.

Edit to add: oops, I forgot to mention that peroneal tendonitis is often related to hindfoot instability because the peroneals are part of the "stirrup" muscles that support the arch of the foot and act at the ankle sort of like the brace you were wearing. They may be getting overworked trying to stabilize you or you might be pronating from the sprain and yanking on those muscles a lot.