Hey, I don't know, but I'll share how I'd start investigating such a question, hoping that would help.

I'm not a professional who does such analyses (so maybe others will correct me), I'm replying as someone from the community trying to be welcoming.

So,

One way I'd look at this question is "how much benefit would I get from investing an extra $1 in Hemp". This is going to split into two sub questions: "how much benefit do I get" and "how much does it cost":

First sub question: What is the main benefit (the most important bullet point). 

For example, is carbon capture the main benefit, or the vitamins? My prior is: It would be very surprising if the "amount" of benefit I got from each of the bullet points was roughtly the same; usually there's an 80-20 situation where 80% of the benefit come from one of the bullet points. (For example: at least 80% of the benefit of growing a banana is for food, even if it does a bit for carbon capture and even if banana fields do look cool). So with Hemp, instead of considering 10 different benefits, I'd try to pick the top one.

The next sub question could be "how much does it cost to grow more Hemp (plus do whatever's needed to get that main benefit, such as produce the plastics, I assume that costs money too)"

And then we have a rough guess at cost effectiveness. If it seems in the vague area of "well maybe, it doesn't look 1000x less effective than an alternative", then that might be a hint to look some more.

Another very different question I'd ask is "if Hemp is so good, why doesn't anyone grow it, sell it, and make lots of money?" (for more on this way of thinking, see Inadequate Equilibria)