Just to clarify after season, or if you graduate early, you can convert ALL your Tuvala gear to boss gear correct? 

You can convert one tuvala item per slot to boss gear. 

This does not apply to accessories though, so its just the 7 gear pieces you can convert.

To be more clear:

Once per season, when you convert a season char to a normal char, you get one boss item convert coupon.

With one coupon you can convert one item from Tuvala to Boss.

No matter if you use the coupon or not, you will get a new one, if you create and convert a new Season char in the next season.

So you can also collect them until you can convert a full set.

Sorry but what do you mean? Full set? Full set of armor?

At the risk of muddying the waters a bit: the one-per-season boss gear coupon converts an item to its equivalent boss gear (one enhancement level lower than the Tuvala item) that can be enhanced in the same way as normal boss gear. So, for example, TET Tuvala armor is changed to TRI DIm Tree armor.  

There is another Tuvala to boss gear exchange path to get guranteed PEN boss gear.  The NPC Jetina will take PEN (only) Tuvala and convert it to the equivalent TET boss gear.  This gear is only enhanceable using the guaranteed PEN reform stones process.  You can exchange all gear items at once if you like, or work on them one at a time, or something in between.  This path also lets you choose which type of boss gear for each slot (dim tree/red nose armor, giath/griffin helm, muskan/urugon boots, bhegs/leeburs gloves).  Weapons are whatever was exchanged for that slot. Edit - correction: can choose Kzarka/Offin for main, Kutum/Nouver for sub. You can only do one exhange per slot per family (the coupons mentioned above do not have this limit).

The Jetina exhchange can also be peformed on TET boss gear, for those who want to choose the alternate enhancement path, but it's still once-per-slot-per-family.

Boss gear obtained using either of these methods is not sellable on the CM.  However, if you convert the armor or helm to fallen god, that will be sellable.

Thank you, last question. Are these items, on either path of conversion, usable with my other characters or do they become bound?

Armor pieces are usable on any character.  Weapons are class-specific, although a few classes share the same weapons.  Otherwise you need a weapon exchange coupon to switch (acquired various ways).  Weapons are not bound, however, so if you have multiple characters of the same class they can all use a particular weapon (using storage to swap, for example).

There is a character tagging / weapon copying system that works between most classes (issues with Shai).

Some types of weapons can be re-boxed and opened on another class.  I can't think of a way to do that with boss though.

Full set of armor and/or weapons.