Clicking the "use" button transfers the token data from its ..... place of purchase .... to your "Token Bytes Available" data bucket.
From there they will be used automatically when all of your Anytime Bytes are depleted.
It is worth noting that if you have Token Data still remaining when your monthly refill occurs you will not lose that Token Data. It will just sit in your "Token Bucket" until needed.
No. They act just as Anytime and Bonus Bytes do. It might just be the occasional slowdown or something. I hope it speeds up for you.
It would be best to start your own post if you would like to receive help with your issue. It would also help to run some tests as outlined in the first response (the one by Liz) and post your results in the new post.
As for data usage, with a capped service one has to adjust things so they use as little data as possible.