On: Did English ever have a formal version of “you”?

[tunesmith]

Cool.

Singular: Thou would like Bob to give thee thy ball. It is thine, and then thou will feel good about thyself.

Plural: Ye would like Bob to give you your ball. it is yours, and then ye will feel good about yourselves.

Not really sure how to ask "Are you okay?" of a singular person, though...

[evincarofautumn → tunesmith]

You need to change the conjugations as well.

Thou wouldst like Bob to give thee thy ball. It is thine, and then thou wilt feel good about thyself.

Art thou okay?

Generally thou forms ended in -st or -t: do/dost, are/art, shall/shalt, go/goest. Third-person forms ended in -eth: do/doth, go/goeth.

[cron → tunesmith]

In Ireland it's fairly common for people to use "you" as the singular and "ye" as the plural. It's less ambiguous but definitely not considered proper.

[Todd → tunesmith]

Art thou okay?

[blafunke → Todd]

Art thou of good contenance this day?