Tough question!
Bills: as far as I am aware no one is sure of the difference between the various types of bill. Even agricultural bill-hooks come in many regional styles. However, I gather that a black bill was a military type. According to Silver himself the black bill is a "weapon of weight" i.e. typically 5 to 6 feet long and fairly heavy, while the forest bill or Welsh hook should be 8 or 9 feet in length and presumably lighter. Welsh hooks were, unsurprisingly, associated with Welsh people, and I get the vague impression that they were often carried by unsavoury types - swashbucklers and bully-boys.
This Netsword thread has a picture of a Welsh hook, albeit from long after Silver.
I'm not sure whether forest bill and Welsh hook are the same thing or not - I suspect they are slightly different - but clearly they can both be used the same way, to hook, cut, and thrust.
A Morris pike is just a regular (15-18 foot long) pike of the time, while a half-pike is just a shorter version, pretty much a regular spear - for Silver, 8 to 9 feet long preferably.
The javelin is a tricky one - according to Florio partesana, lancia, giavellotto, spontone, and spedo can all be translated as javelin! The English version of DiGrassi renders spiedo as javelin. Cotgrave says a iaveline is "a weapon in size between a pike and a partisan." In heraldry it is a barbed spear.
DiGrassi says that the javelin is much like the partisan, but "hath small force in the edge", so presumably has a lighter, narrower head.
IMHO then it is pretty much a spiedo or spetum, but in any case a spear-like stabby polearm with lugs or wings of some sort, similar to a boar-spear or partisan.
As for glaive and partisan, yes, I think they are as commonly meant.
Cheers
