We can't explain the universe, just describe it; and we don't know whether our theories are true, we just know they're not wrong. >Harald Lesch
When you post triggers you should really explain what they are doing.
I don't know where to start - I just don't know what exactly you're trying to do.
I will just post a generic max HP trigger set in the hope you can find your mistake if you have something to compare with:
Trigger: Heal 10% on level 1Player Force
Conditions:
Current Player brings at least 1 [men] to 'heal'
Current Player brings exactly 1 death of <UNUSED unit>
Actions:Set HP of All Units of Current Player at 'heal' to 10%
Preserve
Trigger: Heal 20% on level 2Player Force
Conditions:
Current Player brings at least 1 [men] to 'heal'
Current Player brings exactly 2 death of <UNUSED unit>
Actions:Set HP of All Units of Current Player at 'heal' to 20%
Preserve
... etc. for all Levels
An then:
Trigger: Set LevelPlayer Force
Conditions:
Current Player brings at least 1 Civ to 'max HP +'
Current Player has suffered at most 9 deaths of <UNUSED unit>
Actions:Kill 1 Civ at 'max HP +' for Current Player
Set deaths Add 1 death of <UNUSED unit> for Current Player
Preserve
<UNUSED unit> can be any unit that is not appearing in the map. A good one would be Neutral - Neutral - Cantina. Rename it to 'HP LEVEL'.
As a variation you could create actual units somewhere instead of raising a death count. Looks less professional but the player can easily see his HP Level.
Another modification that you seemed to try would be to heal the unit upon level up. But this needs 1 Levelup trigger for each level, instead of 1 Levelup trigger total.
Trigger: Set Level 2 and healPlayer Force
Conditions:
Current Player brings at least 1 Civ to 'max HP +'
Current Player has suffered exactly 1 deaths of <UNUSED unit>
Actions:Kill 1 Civ at 'max HP +' for Current Player
Set deaths Add 1 death of <UNUSED unit> for Current Player
Set HP of All Units of Current Player at 'anywhere' to 20%
Preserve
Trigger: Set Level 3 and healPlayer Force
Conditions:
Current Player brings at least 1 Civ to 'max HP +'
Current Player has suffered exactly 2 deaths of <UNUSED unit>
Actions:Kill 1 Civ at 'max HP +' for Current Player
Set deaths Add 1 death of <UNUSED unit> for Current Player
Set HP of All Units of Current Player at 'anywhere' to 30%
Preserve
... etc. for all levels