It is, to say the least, not obvious that Constantine's conversion to Christianity was the thing he did that had most impact on commerce in the Roman Empire. Y

It is, to say the least, not obvious that Constantine's conversion to Christianity was the thing he did that had most impact on commerce in the Roman Empire. You did indeed mention "three aspects". But merely mentioning a thing proves nothing. For instance, you say that the Roman Empire's adoption of Christianity had an effect on the practice of slavery, which had an effect on commerce. Plausible, for sure. But Christian Rome didn't abolish slavery or slave-trading, or anything like that. Do you have evidence that what changes Christianity brought to the institution of slavery in the Roman Empire actually harmed its economy? Again, you mention lending. Many Christians have been opposed to lending at interest, or to lending at (what they see as) excessive interest. But so far as I can tell the Roman Empire did not abolish or greatly restrict lending when it became Christian. Constantine himself set a maximum interest rate of 12%, which doesn't seem unreasonably low, and it seems that that stayed in place for at least the next couple of centuries. (And, in particular, until after the fall of the Western empire.) So I think you need more detail and more evidence for the claim you're making. Also: "Christianism"? The usual term is "Christianity", as I'm sure you know. People sometimes make a distinction between "Islam" the religion and "Islamism" the political ideology, but if you make a similar distinction then it seems to me that what the Roman Empire converted to was Christianity rather than Christianism. Are you making that distinction, or some other distinction, or are you just hoping that your choice of wording will annoy Christians? (I am not a Christian and think it's very plausible that the Roman Empire's adoption of Christianity was bad for it and for the world. Also, possibly, for Christianity. So I'm not making the criticisms I do out of a desire to support Christianity and suppress criticism of it.)