[RPG] How to make a Deck of Many Things

What you posit is reasonable except for one thing: The Deck of Many Things has a random outcome that the DM determines by a die roll.

As a magical artifact, I would say that it consists, as a whole of the cards it contains, not of a bunch of independent magical cards. The whole Deck itself is the magic item here, not the cards themselves, they are just pieces/components of the larger artifact. So the individual cards do not necessarily have an independent existence outside of the deck, nor any independent, fixed or specific order inside of it. When a character draws a card it is "randomly" determined by the Deck.

And this element of randomness is very important to the artifacts nature and being (in fact I would say that it is the central attribute of it). So, technically, the DM should re-roll the die if the draw/turn gets re-set, not just play it as though there now (or ever was) any specific pre-determined card on the top of the deck. (of course that's up to the DM).

Look at it this way: If a party engaged in combat resets the turn with Forced Dream, is the DM going to say that the turn gets played over, but everybody get's exactly the same attack and damage rolls as the first time? Or does the DM rule that everything has to be re-rolled fresh and as it happens? My guess is most DMs would say the second, both for combat and for the Deck. Which means that while Forced Dream could be used to avoid a bad outcome from the Deck, it could not be used to then force that same bad outcome on someone or something else: it gets a new random roll.

Indefinitely

He is almost certainly still alive:

You disappear and become entombed in a state of suspended animation in an extradimensional sphere.

Emphasis mine.

Suspended animation is usually understood to mean that you are unaffected by (and unaware of) the passage of time - neither starving nor aging (and thus not dying of old age). From the Wikipedia link above:

Suspended animation has been understood as the slowing or stopping of life processes by exogenous or endogenous means without terminating life itself.

I should point out that technically, suspended animation can be as limited as hibernation, in which case body processes are slowed, but not stopped, and so given enough time, the person may age/starve and die.

However, it is more likely that the intent is for that of the usual SciFi/Magic interpretation of suspended animation where time does not pass. This is indicated by the Sequester spell, which clarifies "suspended animation" a little:

If the target is a creature, it falls into a state of suspended animation. Time ceases to flow for it, and it doesn't grow older.

Again, emphasis mine.