Elven Long Bow Question (in General)

"When used with Archery, you have the chance of hitting in all 5 rounds of ranged combat, that is, 100% Chance-to-Hit (CTH). Without Archery, you have a 20% CTH."

I've missed before with Archery, do I have to have a certain amount of points in archery still for this to matter?

Also I have helm of clearsight so technically I have 6 Rounds, does this still apply?

What that means is if you don't have archery, then it subtracts 80% of your total chance to hit, leaving you with only 20. However, if you train archery to 1.0, you have your full chance to hit, but it is not 100% chance to hit as in you are guaranteed to hit. It's a weird way of saying "we won't penalize you."
Archery applies in all ranged combat rounds, including those granted by the HoC.

I forgot to provide examples. If I remember correctly, the ELB has a base 200 chance to hit. If you train archery, you have 200 CTH, excluding your PTH granted by the weapon itself and the chance to hit given by dex bonuses.
So if you have a +0 ELB and 20 dex, have archery trained to 1.0, and you are fighting a minion with 20 dex and without evasion trained (or equipped DBs), you are guaranteed to hit twice in that round (I think, someone correct me if I'm wrong).
If however you do not have archery trained, you have 40 base CTH (200 * 20% = 40).
If we insert 40 PTH into the above situation, you will only have 40% chance to hit the enemy minion, and you will not shoot twice.

While the pth formula in the wiki probably wrong...

If we use it,

"So if you have a +0 ELB and 20 dex, have archery trained to 1.0, and you are fighting a minion with 20 dex and without evasion trained (or equipped DBs), you are guaranteed to hit twice in that round (I think, someone correct me if I'm wrong)."

Would probably be "So if you have a +0 ELB and 40 dex, have archery trained to 1.0, and you are fighting a minion with 20 dex and without evasion trained (or equipped DBs), you are guaranteed to hit twice in that round (I think, someone correct me if I'm wrong)."

On the other hand, with equal dex, then the ratio of your dex to theirs would be 1:1, and so equal to base chance to hit for the weapon. Which would make it 100, for ELBs, if I remember right.

Also, if you add 40 PTH, you add another 40 to the 200 you already have.

How exactly archery fits into this, the wiki does not say.

x = multiplier = 0.2 + effect * 0.7 (0.8 for ELB)
Final Base CTH = x * weapon base CTH (caps at 89.1 for MSB, 100 for ELBS)
Final PTH = x * weapon PTH. Thus, MSB + are only worth 90% of ELB + at max archery.