Contrivance of the guy who is STILL a drug addict is weird and

I just commented on this is another thread. The writers want to keep the drama of his struggle with heroin addiction. So within the context of the story you could either say Phillip can beat it on his own and their limited capability for synthesizing future medicine is needed for other things, or for whatever reason the Director wants him to conquer the habit without a magic cure. Take your pick.

These people have done extensive research not only into their identities but the time they will be going to. I'm sure seeing it all around them for real is quite a different experience from their training, but they're not entirely unprepared for it either. Suppose you studied the Middle Ages in great detail; speech, dress, contemporary culture and attitudes, all that. It would still be surreal finding yourself there but there's a reasonably good chance you could fit in and do whatever you were sent to do without other people thinking you were too weird. Claiming to be from a place fifty or a hundred miles away would probably be enough to cover any minor oddities. Even more important back then, when bad things (often involving fire) could happen to people who seemed too weird.

They do have some ability to construct devices based on their tech. You'll see a few examples in later episodes. But that capacity is clearly limited, the items are distributed and used on a priority basis and only when necessary. Every piece of hardware floating around out there risks the locals coming into possession of advanced technology - and perhaps mounting a serious effort to determine where the hell it came from.

In think the asked him first thing if he wanted methadone.

Even if the Travelers inherit some of their hosts consciousness (which they don't do a very good job of explaining), Philip's addiction should largely be confined to dealing with the physical manifestation (cravings, etc). There are entirely conventional therapies for switching addicts to maintenance drugs (buprenorphine or methadone) which you'd assume they would switch to, and assuming they couldn't obtain them in the 21st they seem to have the tech and know-how to synthesize them or even more superior alternatives.