testing stuff out in my own little page, ignore this probably.
Round Start
Primary Threats: 2P
GuardLowStartup7Recovery11Advantage-3 and j.2K
GuardAllStartup10Recovery9 after LandingAdvantage-
Primary Options: 2K
GuardLowStartup6Recovery12Advantage-3, 5K
GuardAllStartup7Recovery10Advantage-4, and 2D
GuardLowStartup10Recovery18Advantage-19
Round Start Matrix 
Option
Faust's Round Start
2P 5K 6P j.2K 5K Countered Trade Punished Counters 2K Counters Neutral (+2) Counters Whiff Punished 2D Countered Counters Counters Countered
Very advantageous round start as Jack-O's 2K's speed, range, and low profile frames make it incredibly difficult to stop or punish, especially by Faust. Faust has no normals he can immediately press that outright beat Jack-O
2K, all of them either getting hit during their start up or just missing, usually leaving Jack-O' plus thanks to 2K's fast recovery. The only thing Faust can reliably do that beats 2K is jump in the air and immediately j.2K to punish 2K's recovery, which has incredibly low reward. Faust's j.2K inputted immediately after jumping is barely plus. If Faust attempts to cancel in Love or Mix Mix Mix, Jack-O will recover in enough time that she can successfully 6P either follow up. Not canceling j.2K and just landing isn't much better, only leaving Faust +2. Faust's strongest way of punishing Jack-O 2K is by manually timing a whiff punish, which is easier said then done. Jack-O' low profile state lasts right up till the end of her recovery, meaning any good high poke Faust has (5K
GuardAllStartup7Recovery8Advantage-2, f.S
GuardAllStartup12Recovery20Advantage-8, 5H
GuardAllStartup13Recovery18Advantage-7) is already unusable. Faust's best whiff punish is standing still, letting Jack-O's 2K whiff, and then punishing with 2K > 2D before her foot retracts. The most reliable easiest whiff punish Faust has is 2P, which leads to nothing, and is 0 on hit. Do 2K until Faust stops playing round start.
In case Faust decides that he's okay with the low reward of divekick, you can easily call him out with Jack-O's 5K.
5K > dc > (delay) c.S > 2H > 236P > 5K > dc > c.S > 2H > 236[P] > Dash > Forward Jump > j.hs.6X > j.S
This combo has does 139 damage and builds a solid chunk of meter all while taking Faust to the corner. Once cornered it's going to be very easy to build up the final bit of meter you'll need for Cheer H
GuardStartup3RecoveryTotal 15AdvantageSee Notes, and from there Faust is going to be really wishing he didn't divekick.
There's a slight delay before doing c.S. If you're too early you'll do f.S instead, too late Faust will fall down too much and the 236P > 5K link will no longer be possible. You just have to eyeball the timing but the window is pretty big.
At the point Faust is either blocking or trying to whiff punish you round start, begin representing 2D to call him out on any attempts to stand still and let you whiff. Faust's ability to crawl would be useful in this scenario as he is the sole character that can move backwards for whiff punishes while blocking any surprise lows, if not for the fact that if the Faust down backs at round start then proximity guard activates on Jack-O 2K in spite of the fact it whiffs if he just crouches normally. From here rotate your options as needed, just make sure to start with 2K.