when I read it first, I thought its perfect. But later I found something is odd here. Out of 4 observations which you have made in each category, first two seems to be going good with the venn dig. but when it comes to 3rd and 4th, I think we need to change the representation may be.
if L is recursive then M may or may not be recursive. This makes sense because there is RE language which may not be recursive.------- (case 1)
if L is RE then M may or may not be RE. this also make sense because set of languages is bigger than set of RE languages.
if L is decidable then M may or may not be decidable. How is that possible. M is a bigger set. If it is decidable, then how can anything inside this set can be undecidable. that means, if L is decidable then M can not be undecidable, so the other option left is decidable. In case 1 recursive languages are also RE, but here a decidable language can not be undecidable at the same time.
similerly with 4th observation:
if M is not recursive then L may or may not be recursive. this looks right because here M could be RE and so L can also be RE, but not recursive.
if M is not RE then L may or may not be RE, again doesnt look good for same reason as described above. L is inner entity of M.
if M is not decidable then L may or may not be decidable. if M is not decidable and suppose L is decidable, then L is both decidable and undecidable at the same time.
But about your analogy regarding addition and multiplication, I cant really comment on it. It looks correct to me, but only if we dont represent it via venn diagram. I think if we consider that multiplication is made up of many additions, that is multiplication is derived from addition, then your analogy may suit it.
Let me know what do you think about it.