Welcome to MTGO! Glad to have you.
- In most cases you want to leave the Traps in the SB against Xerox and just lean on the discard, Flusterstorms and Defense Grids. The problem with Traps is that you game plan is basically trying to limit the amount of interaction the opponent has access to during your turn between the discard and Defense Grids - your opponent can't cast multiple spells if you have a Grid in play and likely won't have multiple counters if you've been stripping their hand - so Trap is accomplishing the opposite of what you want it to do. Board it in against PO and the Mirror. I also like it against Shops because after you Hurkyl's them, they will generally play out their threats first and then let you trap whatever their prison piece is. That depends on the exact list and SB configuration though.
- If you really want the sweeper effect, Deluge is probably your best bet. However, SB space is limited. In general, the dealbreaker on Toxic Deluge is the lack of utility of the card. Karakas is an extra mana source against Shops and a discard spell against Control/Combo decks. Fatal Push also has some function as removal against Shops (hitting Revoker) though I've honestly cut it for another Brutality. The problem with Deluge is that it's only really good at dealing with these hatebear/eldrazi matchups and that in my opinion isn't enough to justify the SB slot. Now, your experience may vary. I'm a nerd so I keep track of my matchups and I see that over the past month I played against Eldrazi 4.5% of the time, "Fish" 6.3% of the time, and a couple Humans decks (like <2%). Conversely, Xerox + Survival has been ~35% of my matchups, with Shops another 10%. Having Karakas and Brutality are then more valuable because they do more in those matchups.