Question 1:
I see a new subscription can be had for just $149 – that’s almost $90 less than I am paying now! What do I do to get this? Do I first have to cancel my existing Subscription. Or does my current subscription continue and just roll over into the lower price. Also – is that promo amount deducted monthly, as my current subscription is, or is this a one time payment for the entire year?
Yes, you need to cancel your current one, or you will end up with 2 subscriptions. This is an annual payment for the whole year.
Question 2:
If I subscribe to a new subscription at this lower cost – do I lose my unused Substance share points?
You probably mean Source points. You keep them

Question 3:
How does the buy out option work If I choose to no longer subscribe at all? I see another offer that says MAINTENANCE UPGRADE Substance Painter & Substance Designer for $50. Does purchasing that automatically get me my perpetual license, or is there another route I have to go through to get perpetual buyout licenses for those two programs. If so – how much is that and are they being promoted at a lower price as well.
I have read about perpetual being offered on Steam – is this the only way to redeem my buyout offer or, having been an Algorithmic Subscriber for over a year, can I get my perpetual buy out programs directly from Algorithmic / Adobe? I have never used Steam and do not want to.
The rent-to-own option is on your monthly subscription. You can use it, at the moment when you cancel, if you have been subscribed for more than 12 months. If you don't have 12 months at the moment of cancelling, or refuse the option when cancelling after 12 months, then you lose this option.
Question 4:
Do I need to purchase the buy out perpetual licenses immediately upon canceling my subscription, or can I wait till October 2020 even if I no longer have an active subscription? For instance, I sign up for a new subscription at the lower price but want to wait till October 2020 to exercise my buyout option as granted under the previous subscription?
I answered it above. The rent-to-own needs to be exercised at the moment of the cancellation, if you meet all the criteria.