Battlescript variables...

$3DAC : Unique monster variables (1 for each monster)
$3DC0 : Counter for how long monster has been alive (2 bytes)
uhm... where's the space to something like 383 variables, considering that after at least 0x14 bytes there's already another thing? i mean, that surely happens, so i wonder how they store them...

When it says 1 for each monster, it means 1 for each of the 6 monsters in the current battle. Not one for each type of monster in the entire game. There's actually a variable for each of the 4 character slots as well, so...

$3DAC is for character 1
$3DAE is for character 2
$3DB0 is for character 3
$3DB2 is for character 4
$3DB4 is for monster 1
$3DB6 is for monster 2
$3DB8 is for monster 3
$3DBA is for monster 4
$3DBC is for monster 5
$3DBE is for monster 6

2 bytes for each variable * (4 characters + 6 monsters) = 0x14 bytes total. If you look through the RAM map, you'll notice that many things are spaced 0x14 bytes apart. This is why.

Anyway you say the RAM area used for battle is the same space used for maps? in other words it would be necessary to save them into another area and load them before a fight?

Yep