This reply is only an answer to the first post.
Fire Mastery will improve Shield of Fire's healing a lot
Actually Fire Mastery increases all magic type abilities damage, but there are some exception. Also Fire Mastery will increase Spell Book Spells damages.
Shield of fire will heal more than any of the other healing spells, including Fradz's
Spell book spells heals even more.
# Fradz's healing spell would only heal (speculation on stats) 688 hp and 440 mana, at lvl 20 and no lightning mastery
HEAL ABILITIES
Hydro Shield: (abilvlx10)+(intx0,5)
=> Lvl 1 & 50 INT: (1x10)+(50x0,5) = 35
=> Lvl 10 & 250 INT: (10x10)+(250x0,5) = 250
Blessing of Lightning:
- Stats (abilvlx5)+(agix0,1)
- Hp: (abilvlx100)+(strx4)
=> Lvl 1 & 50 STR: (1x100)+(50x4) = 300
=> Lvl 10 & 250 STR: (10x100)+(250x4) = 2000
=> Lvl 20 & 500 STR: (20x100)+(500x4) = 4000
- Mana: (abilvlx50)+(intx2)
=> Lvl 1 & 50 INT: (1x50)+(50x2) = 150
=> Lvl 10 & 250 INT: (10x50)+(250x2) = 750
=> Lvl 20 & 500 INT: (20x50)+(500x2) = 2000
Speedy Boost:
- Agility: (abilvlx10)+(agix0,2)
=> Lvl 1 & 50 AGI: (1x10)+(50x0,2) = 20
=> Lvl 10 & 250 AGI: (10x10)+(250x0,2) = 150
=> Lvl 20 & 500 AGI: (20x10)+(500x0,2) = 300
- Hit Point Regeneration: (abilvlx8)+(strx0,2)
=> Lvl 1 & 50 STR: (1x8)+(50x0,2) = 18 / SEC (270)
=> Lvl 10 & 250 STR: (10x8)+(250x0,2) = 130 (1950)
=> Lvl 20 & 500 STR: (20x8)+(500x0,2) = 260 (3900)
- Mana Regeneration: (abilvlx4)+(intx0,1)
=> Lvl 1 & 50 INT: (1x4)+(50x0,1) = 9 / SEC (135)
=> Lvl 10 & 250 INT: (10x4)+(250x0,1) = 65 (975)
=> Lvl 20 & 500 INT: (20x4)+(500x0,1) = 130 (1950)
Attack Speed: - 25%
Movement Speed: - Max mov spd
# In later chapters you won't be using Phodom's spells that much thus rendering Fire Mastery useless
Depends how you play the game.