1. Kids can only trade for a single card. In my playtests, I noticed that there's little reason to trade for multiple cards, as you generally only want the bigger cards. Additionally, having each kid trade for a single card makes it so Spiff isn't always the only kid going to the playground. The only kid who can get multiple cards is Jessa, as her ability allows her to steal a card without trading.
2. Yes, Pocketed cards are locked in. You get to keep that card since Spiff is technically not holding it. The only way to lose cards and bucks through unfriending should be during the First Subs event.
3. Usually, nothing happens to bet ego. The Special card effects will mention what happens to it, but otherwise you just get it back/no actual ego is lost. Mechanically, each location outside the alley allows you to easily maintain your Ego so you can keep your friends. Going to the alley makes it very risky as you could either lose a few friends or lose a bunch of Ego when you're not ready for it. So for your examples:
- Carl card is pulled, "After this duel, lose 15 Ego. "
Win or lose, you lose 15 Ego. Final Ego: 5
- Lumby But Giga card is pulled, "Lose 1 Buck for each Ego you bet. If you cannot pay the full amount, you cannot gain this card."
Win or lose, your Ego is not affected. This card only affects Bucks, so you lose 10 Bucks or all of them if you have less than 10. Final Ego: 20
- Both Of Griswald's Knees card is pulled, "Lose the Ego you bet, then reduce the amount of bet Ego by half."
Win or lose, lose the Ego you bet (10 Ego in this case). Final Ego: 10
- Baby Filkiss card is pulled, "Immediately gain the amount of Ego you bet."
Win or lose, gain the Ego you bet (10 Ego in this case). Final Ego: 30
- Dirk Canyon, Esquire card is pulled, "If you win this duel without betting Ego, gain 10 Ego. Otherwise, lose the Ego you bet."
If you win/tie: Ego was bet, so you lose it. Final ego: 10
If I lose: No Ego is lost. Final ego: 20 WAIT! I was wrong on that! "Otherwise" refers to any case where you didn't win without betting Ego. So if you lose, whether you bet Ego or not, you still did not win. Final Ego: 10
- Dog Bower's Dad card is pulled, "Reduce the amount of Ego bet by 10. If you tie or lose this duel, lose the card you dueled with."
Win or lose, your Ego is not affected. This card only affects what happens to the card Mindy is holding. Final Ego: 20
I keep forgetting to mention what happens to bet ego in the rulebook. This has come up a few times in playtests with friends and I just never put it in my notes. Thanks! I'll update the rulebook now