In relation to your insurnace, a very quick reading of the policy seems to show the following:
https://www.americanexpress.com/content/dam/amex/au/benefits/Platinum/Insurance17July2018.pdf
Cover 1.
In the event of Travel Disruption In the event of Travel Disruption, We will pay:
(a) non-refundable deposits;
(b) pre-paid excursion costs;
(c) travel agents’ commission, which is limited to $750 or 15%, whichever is the lesser;
(d) unused travel and accommodation costs that You have paid or are contractually obliged to pay;
(e) any other reasonable additional expenses incurred limited to $5,000;
(f) the retail price for any ticket (or part thereof) of a Licensed Airplane, Ship or Bus ticket purchased using American Express Membership Rewards or similar reward points or Travel Benefit if that ticket is subsequently cancelled as a result of Travel Disruption and the loss of such points cannot be recovered from any other source;
(g) up to $30,000
So they will pay you the retail value if you can't get the points back, but it seems you will get a refund of the points from SQ so that may not apply.
Your travel insurance might however arrange for tickets to get you back back home anyway. I would contact them to ask what they advise.