Yes Malakai is Biblical. Infact all the names in the name generator are taken from the Bible, classic literature, or Roman history. Course some of then names they made themself and are using the ones they found amusing from their own Black Library sources. Names such as Jagadei Khan (Primarch of the White Scars).
As for all your questions about your manic chainsaw toting buddy.
1) Books in the 41st millienia vary, paper, parchment(animal skin), leather bound, vinyl bound, hide bound, scroll form, etc.
2) If the weapon states it is one handed or balanced the user can carry the two weapons, however he msut be trained in two handed fighting / ambidexterous.
3) Prayers can be found all over the web or in classic referance books such as the "Imperial Guard's Uplifting Primer" by black library I would post the ISBN but I cant seem to find it on my copy.The book talks about proper procedures of being a guardsman and is chualk full of useless info, as in its progpganda and is lies to the average guardsmen. Like, "Concentrated Lasgun fire will take down flimsy Eldar tanks".
here are some sample prayers contained in it.
The Emperor's Prayer:
Adore the Immortal Emperor for he is our protector. Admire the Immortal Emperor for his sacrafice to mankind. Exalt the Immortal Emperor for his strict guidance. Revere the The Immortal Emperor for his undying guard. Venerate the Immortal Emperor for his holy wisdom. Honor hte Immortal Emperor for his eternal strength. Glorify the Immortal Emperor for his all-seeing vision. Praise the Immortal Emperor for his unending rule. Haile the Immortal Emperor for he is the lord and master. Worship the Immortal Emperor for without him we are nothing.
Prayer for Safe Return
O Eternal Emperor, Who alone watches us, and rules the tides and storms, be compassionate to your servants, preserve us from the perils of the warp, that we may be a safeguard to the domain of men.
Incantaion of battle (to be shouted and repeated during combat)
Smite the foe! Smash the enemy! For the Emperor we bring Death!
and many more.... Tis a funny read