Make a save state and then open that save state in a hex editor (I recommend CrystalTile2: http://www.romhacking.net/download/utilities/818/
); once you have it open I want you to try and see if the english names of your party members appear _anywhere_ on the far-right side of the editor: i.e press CONTROL + F and enter any of your characters names and if we're lucky then they will appear.
I'm going to assume they do, because I have never edited this particular game so I don't know if they do or not; once you find one of your characters you are going to look hard at each of the hexadecimal values on the middle-portion of the editor. Under each name all of that characters data will be represented except it won't look recognizable. The fastest way to find the two-number value (example: 01, AF, etc) that represents a character level is to find one of your characters who is (EXAMPLE) at level 5, and then make sure you have at least 2 or 3 more characters ALSO AT LEVEL 5. Why? Because you're going to eye-ball all of the hexadecimal values, i.e. the "pairs" of numbers in the middle of the editor and you will try to find which hex value is REPEATED ON ALL THREE of the imaginary characters I'm describing in this example.
It might look something like this:
May 02, 2016, 12:06:33 pm - (Auto Merged - Double Posts are not allowed before 7 days.)
That screenshot is from the save file of the game Elminage: Gothic, an RPG, and I have it open in CrystalTile2. As you can see the file begins immediately with my party members, and below their names, i.e. below "aweigh", is the entirety of that characters makeup: level, age, gold currently in hand, race, class, LEVEL, skills, etc, etc. Some examples...
On the hexadecimal portion of the editor try to eye-ball/find the value "0A" in the offset address (the numbers on the FAR LEFT) 000000A0. You'll find it in the hexadecimal column "0C". It is not surrounded to the left/right by anything else other than 00's, so you should find it easily. That value, 0A, is the character aweigh's Defense number. On another chracter (if you were to keep scrolling down) it might be say 0A but whatever their Defense hex-value is it will be in the same place, generally speaking. It might differ somewhat in Tactics Ogre of course, but the principle is the same.
The only way to find out what value means what when you don't know and there is no online tutorial for your specific game (as in your case, and as it was with me with Elminage) is to pick some values that look "likely" and change them. For example I recommend picking lone values, or at least in the case of Elminage the ones off by themselves usually represent stuff like what Skill the character uses, or what level he is, or what CLASS he is, etc. The long rows of many hex values usually represent other stuff. Think about it this way: how many values would a programmer need to represent.... Level 5? Exactly.
Now you go and change them, load up the game, and see if something changed. Eventually you'll find the value (or values) you want.
Sometimes there are some things that can be self-evident. I want you to eyeball that image again and spot where there is a long row of 03 03 03 03 03 03. Saw it? Ok, that represents the amount of spells the aweigh character has on six spell schools in the game. He has a max 3 spells on schools 1-6. I'm not saying it's hard to miss a detail like that but, I want you to keep in mind that sometimes the hex value is represented "naturally" and is self-evident. I.e. if you are looking for level 10 it just might very well be a 10. Who knows!
Post again and take screenshots if you need any more help with this.