1) I think an online advertising growth strategy will be hard, or really any strategy that strictly involves spending X in advertising for the recruitment of Y in revenue spend. However, people that use drugs talk to each other about where to get drugs and treatment (surprising, I know), and I would build your marketing strategy around word of mouth and patient to patient referrals. Initially reaching these communities are hard, but I would really think about how well the product can be optimized for patient -> uninitiated patient referrals, similar to "growth loops"
That said, I've worked in a start up with a similar premise, hire domain experts to give advice to customers during a life transition, and watched it fall down as the operations shook apart and the acquisition cost was very high. It's hard to get both the operations to stay great during the scale out, and keep the the marketing channels diverse enough so when you tap one out, another 5 are in different stages of life.
2) When assessing this product for my own use, the thoughts I had where: 2.1 Is this available in my area? How far would I have to travel initially? 2.2 Do they drug test me like my current place? 2.3 How frequently do I met the doc/what's the script duration? 2.4 What is expected of me to stay in MAT?
Basically, I have a provider, but with more up front information, might be willing to switch. However, the website and FAQ are pretty sparse, and I really don't feel like picking up the phone to talk to someone (flatmates, ya know?), so I feel like that's kind of a blocker.
Good luck!