I'm here, I'm here... 
Fizzy
I'm assuming the Tret is prescription and even if it isn't I really can't comment on that.
Can I ask why you're coconut cleansing twice followed by another cleanser. Does a single coconut cleanse not do the job, if so I'd really get to replacing this ASAP. Clinique TTDO balm, possibly the Bodyshop Chamomille (though this contains fragrance)?
Routine wise I would consider using the BHA in the AM post cleansing to get a bit more frequency out of it. As I understand it you now do Retin-A on night 1, BHA on night 2, AHA on night 3, unless I have misunderstood.
Yes, serozinc might be useful, especially when suffering from active breakouts.
It's the Verso eye serum if we're going to be pedantic about it. I'll keep an eye on the Skincity advent calendar for you (I usually buy it from there), they might just do a deal on it in the run up to Christmas like they did with Paula's Choice today.
If we're talking Benton snail goop as in the steam cream I'm not 100% confident how this will work for different skin types, it's not super heavy but may only be suitable for night time if you're combo/oily. The essence should be good for all skin types but with the acne scarring in mind perhaps the CosRx 96 Mucin Power Essence as mentioned by Lumpy (iirc) may be a better fit. There's a somewhat pricey ($4) sheetmask version of it too, but have yet to read any reviews on it.
P50 - yes, I do think it would be good for you provided you can tolerate it. I'd offer a decant but I still have yet to restock and am nearly at the end of my own bottle.
With the early rosacae you're in the same boat as Pupsie, so depending on how severe it is you probably benefit from similar products and she seems to be doing well with the PC BHA and BR P50W.
Azelaic acid like Dulci mentioned also crossed my mind but I'd use that instead of BHA, probably not both.
Mandelic acid (poss. peels as an occasional treatment) also worth considering specifically for the acne as it's the only AHA that can penetrate deeper into the pore level (like a BHA) and relieve congestion but you'll have to see how it fares with the rosacea sensitivity. I know SR-skincare sells them for v. little at various concentrations, not sure on that brand as a whole, Lumpy if you're still about didn't you purchase some things from them some time ago?
Which BHA are you considering? The resist or clear version may suit you slightly better, though you can't really go wrong with skin perfecting liquid.
Shrew
I tend to use my strongest active that isn't Retinol after p50, currently that's the Niacinamide which I also use together with the TO Retinoid.