two simple questions.

In my experience, it has been fairly simple. 4.5 INT = 1 MA when it comes to my range.

Yeah, what the calculations are saying is that the ratio will vary depending on your stats. In example, my 134 Mage has 4.2 INT = 1 matt, but I'm pseudo low-LUK with a base LUK of like 95. If I were LUKless and kept the same equipment bonuses, the ratio would be 4.8 INT = 1 matt. I think that in general, possibly, the ratio will stay around 4.5 on average, probably 5.0-6.0 for the well equipped.

Also, on the original topic, I have no idea about the second question. (Hopefully someone else does, and this is to remind everyone that OP asked two questions)

Edit: I just calculated the ratio on my HS mule, which is LUKless, and has ridiculously low magic attack (because it isn't for attacking). It was 8.9 INT = 1 matt. Kind of ridiculous, so my estimate of ranges above really varies depending on whether or not your weapon has a lot of magic attack, and/or you have a lot of INT comparatively. The more INT you have, the higher the ratio (meaning one matt is worth more INT), the more matt you have, the lower the ratio (meaning one matt is worth fewer INT).