2) As a crude cost of points, I'm using a reasonably typical credit card churn cost (rounded up for ease): 90,000 points for $300. This would mean that 8,000 points = $27.
4) With the long-haul flights (revenue), the points accrued matter, too. I ask [how many domestic short hops in Y would I get with these points?] and then mentally discount that from the ticket cost. E.g. SYD-LHR return in flex Y as an SG nets 43,400 points = 5.4 flights (but with 5.4 * $40 = $216 in fees). If an average saving (after fees) per domestic short hop reward is, say, $100 each, then the points accrued from SYD-LHR would be worth $540.
Shouldn't you value the 43,400 points under (4) at $1,432, based on your valuation at (2) of 3.3c per point?