Three thoughts, which partially echo some of the comments already made.
1. Your regulator choice: I agree with tbone - go with a DST first stage, and have two XTX50 second stages. Frankly, I see little / no value in having a turret / swivel first stage for single cylinder, backmount diving. But, the DST is a solid first stage, and a very good choice in the Apeks line. If you elect to go with a 'XTX50' setup - Apeks markets this as a DST first stage and one XTX50 second stage - and choose a XTX40 as the additional second stage (instead of a XTX50), use thew XTX40 as your primary, and put the XTX50 on a bungee necklace as you alternate (as tbone suggests, because the 50 has User Adjustable Breathing, while the 40 does not). The 40, properly tuned, will breath the same as the 50 with the UAB fully open. I personally prefer to dive with identical / equivalent 2nd stages.
2. Your computer choice: While I think the Perdix AI is a nice computer, I question whether that is a cost-effective initial step for a newer diver. AI is nice, as a convenience. I have used it for many years, because it is easy to rotate my wrist to check my gas supply, instead of unclipping my SPG to read it. But, the gold standard is a simple 'brass & glass' SPG, and that should be your primary source of gas supply in formation. At this point, a simply non-AI cvomputyer may be a better way to start, simply to save money. I understand tbone's reservations about Suunto, and I think Suunto has lost sight of the target market with some of their recent offerings (which seem to offer glitz, and extra cost, over functionality). But I think the Zoop is still a reasonable first dive computer, even with a somewhat conservative algorithm. I would look for a used unit, although i appreciate the fact that your geography may not mean that there are a lot of used DCs to chose from. Still, going with a Perdix AI may be more than you need at the start.
3. Your wing and BP) choice: You make mention of the possible benefit of 35lb of lift vs 30 as a consideration in wing selection. For single cylinder diving, I would not give consideration to this. A wing with 30lb of lift is more than adequate. I have both Dive Rite and Apeks wings, and am happy with all of them. I think the Apeks wings (I have an 18 and a 30) are a bit bulky and overbuilt, but that subtlety may not be an issue for you starting out. A question: when you refer to a 'Dive Rite harness', I presume (and recommend) that you are considering a Basic Harness, not a deluxe or Transplate Harness. I do commend you for going BP/W at the start (and going with stainless steel for cold water diving is a good idea). You won't regret the choice.