The main point is that parting shot really doesn’t actually help your plan, (I mean, I get the whole “use hypno, evolve to cancel sleep, parting shot into darkrai” idea, but in practice in can be done with 1 switch or 1 chaos tower/all-night party). A copy of the non-EX-yveltal without the ability could help you setup energy onto darkrai-EX while do chip damage also.
Bursting balloon could be an idea if you generally end up playing against mega decks but really if you choose all-night party they heal and balloon doesn’t pick up the ko; and if you choose to play chaos tower then the sleep flip will make a 50% chance of the balloon being worthless. Of course balloon could setup a ko where if they attack your active, darkrai comes up and OHKOs pretty much anything, but there is another attacker which easily outclasses bursting balloon:
Fright night yveltal: This baby is the bane of all mega decks, nullifying spirit links it can buy time just by being active. Pile a dce and a dark onto it and deal that early damage that will put megas down to OHKO range for darkrai; you can even hit 2 at once! Also, the awkward 130 hp is often not OHKO’d so you can often attack twice, maybe picking off a shaymin-ex while slowing setup and dealing large chip damage to your opponents active! Would probably be as effective as wobb aswell as being able to attack.
max elixir is kind of the card that makes this deck work fast enough to catch opponents off guard. You have actually got a very good energy line up so don’t worry to much about that, it just needs a little speed from max elixir.
wally and brigette are a little gimmicky, and the benefits are vastly outweighed by the amount of times they will be dead cards. Might i suggest you add a level ball to setup the hypno if that often feels difficult and use the space to bump up the lysandre and maybe also the hex (less essencial) to 2. You can lysandre a mon with 2 or more retreat and put fright night into the active and trap it if your opponent relies on float stones to retreat.
Also looking at the list it looks like you are a little too afraid of losing resources to a sycamore (2 super rod; only 2 sycamore). Generally as a guideline, a lot of decks like to max out on sycamore as even if you end up drawing multiples, it still allows you to draw 7 cards (which is amazing!). If you run more sycamore, you will find that vs seeker is more useful when you draw it as it can recover any supporter like lysandre, hex, n or even sycamore, that you discarded earlier. Generally max out on these two cards. (n.b. usually you don’t need more than 1 super rod when the only thing you will probably end up discarding to sycamore ever is a stage 1 of a 2-2 evolution line)
I know this got a little bit long but its probably easier than replying back and forth. Remember don’t take my words to be 100% true, everyone is entitled to their own opinion and there isn’t always a correct or incorrect way in deck building.