Yes the DEC issued is fixed and its slowly going down ... at least that how it was announced a year ago ... started with 1M DEC per day and its somewhere around 880k atm ... will they change the peg in the future ... dont know ... but it will be nice if the game have a higher valued currency ....

Also what happens to the DEC that is used to buy Untamed Packs, is it burned, used to fund tournament prizes or just sold by the devs on the market.

It is not burned .... what are they doing with it is up to them ...