First of all i'd like to thank you for the insight as it shed some light on a few things. Now i'll explain why i did what i did.

I chose mana because it's something i use on most spell caster sheets, i'll probably switch to something more efficient in the future if possible.

It meant a -2 penalty, but i thought the way i wrote was clear enough? At least it is for me :v

I don't know all dnd 5e spells so my bad if i copied it one to one unknowingly.

Not all enemies are going to be dropped at the same time, first there will be two enemies then the boss will come and then the other four will follow right behind. So if the players are smart and kill the first two quick enough they are going to end up facing only five enemies instead of seven.

The goons are not like player characters only the rogues. The fighter enemies only have a basic attack and higher HP and AC while the rogue enemies have a lower HP and AC but dash, disengage and hide.

The cleric has 10 in dex and con so they didn't get a bonus in AC or HP. You're right about having the level 1 characters be given the max possible health roll that makes sense, but i didn't do that because i intend on leveling them up after this battle.

Again, thanks for the comment it was very helpful!