HexCheat:

To use: Hex-edit your saved game file. Be sure to have a decimal-to-hexadecimal converter on hand. If you do not know how to hex-edit files, it is best not to even try.

Offset - Size - Description
94 - 2 - Current HP
96 - 2 - Maximum HP
98 - 2 - Current Mana
9A - 2 - Maximum Mana
9E and A2 - 4 each - Experience points (be sure to edit both
values so that they are the same!)

Note: It is probably best to check how many experience points you need for the next level, and enter that value (minus about 50), in the 9E and A2 double-words. That way, you can also learn new spells and the shops will have new stuff when you gain a new level.

High Constitution:

To get High Constitution keep using a magic spell and keep using it even though you are out of mana. don't be scared if your health goes down. If you use the spell enough you hp will go back up and your constitution will be maxed out