I bought the game multiple times to be able to play duels with daughters. Sadly the 1000 point limit makes it impossible to access the higher level troops and spells. I guess that I could play through the campaign to eventually end up with everything, but considering I'm particularly interested in it right now.
Is there any way to change the amount of resources available to players in multiplayer/Duel?

Isn't exactly what you ask for, but...
If you play at home together, you can try Eador:Genesis
During loading press and hold "B", it would start test battle.
After confirming start of the battle, hold U and press menu button, you will see menu which gives possibility to place any unit on field. Place units, give turn to another player, place units for him.