Super robot wars Z1, Help! (ZEUTH route, Scenario 50, no-upgrade run)

Super robot wars Z (PS2)
ZEUTH route
Scenario 50 - A Human's Heart, An Angel's Dream
No upgrade run.

I can't beat the level.

Turn 1
- go after Sara.
- Sirius appear's.
- attack Sirius.

Turn 2
- Sirius is shoot down
- lot's of bad guys flee
- Sirius is alive with full HP
- go after Gainer

Turn 3
- Gainer shoot down
- everyone goes into the Orguss Battleship
- GUARD for like 5 Turns, and repair HP loss.
- everyone is fully restored.

Turn 8
- Attack Overdevil
- Overdevil HP, less than 50%

Battle Phrase
- Overdevil uses MAP move
- EVERYONE DIES.

I can't survive against the Over devil's map move.

Not every units has evade, wall and (evade + wall).
and the units that can use it, gets hit by the enemy units, before the MAP move attacks.

also, Sirius can 1 hit OK, or leave my units with LOW HP.
so I need to use wall or evade to survive his attack.

Gainer, likes to dodge.
So I need to use Strike.

By the time I get to Over-devil, I have no guys to use Valor or Soul.
and when I do, they have no morale, or out of range.

So can anyone help me.

And .....
Destroying all other enemies before defeating the Overdevl is the SR point.
As in the harder option, so I haven't tried it yet.

Note: What is the Orguss battleship called? I forgot.

Cybuster - No, I am not trying to get the Skill point,
I just said, I haven't tried to get it because I think it's the harder option.

and the OverDevil is the final boss, why wouldn't I use Valor.

also turtling doesn't work against the MAP move. it can attack all my untis and they all die in one hit, In regard to Exhaust, yes it helps but not enough units are kept alive to take it down.