Sundry questions about how things work

1) there are 6 sizes of elemental in the game
a) I cannot find which spells summon which size - I think normal is size 4 and lesser size 2 & nothing summons size 6 except earth attack & that is only earth (duh!)

I think the normal "Average" earth Elemental is Size 4 (From the spell "Elemental". Ice Elementals, also follow this pattern I believe.

b) how do they shrink? - do they reincarnate as the next size down when they suffer "total HP loss" or someting else

Total Hitpoint loss. Sort of like a deathform of a Black Hunter.

2 Do spell & other effects impact on missile weapons as well as melee ones specifically:-
a) fire 9 blessing
b) Weapons of sharpness

Yes.

3 Just how does dispel work.
a) Does it compare ritual cost plus extras to dispel cost (30) plus extras or does it just compare extras?

Just extra's, I believe, but there is some admitted wierdness at certain times of the game with Globals in general.

b)Is there a random element?

Yes.

4 If a weapon says damage 5x10 vs hoburgs does that mean 50 vs hoburgs or that the total damage including strength is multiplied by 10

I don't believe it includes strength, but I could be wrong. But it is a factor of the multiplier in dealing damage.

5 I ritual of returning my Ice devil & he was paralysed - will this wear off? He is 163% heroically fast so I hope so.

The paralyze should have a timer when it wears off. I have seen a Ritual of Returning fire even when someone is exhausted/paralyzed before, but I can't say for absolute certain if it wasn't from other circumstances. It's semi-hard to gauge.