@Walg
Well, if you look at mrdotsgame page, which has DMD (and lots of news about DMD on the front page), there is a page called "Support me!" which specifically states that you can supports development of his game
s on Patreon, and considering he only has two, one could argue that the funding from Patreon goes towards both games at undisclosed proportions. Obviously, as you've said, we don't know his exact finances, but we can make an educated guess by looking at his Patreon, which is where my original numbers can from, and as you've said, there are several additional income sources (one time purchase for DMD on site, buy me a coffee, paypal donations, etc...)
So with the amount of funding he has available, and from the argument that he states that his patreon money goes to supporting both games on his website, my argument is that the proportion dedicated to DMD is decided purely by MrDots, but undisclosed on his Patreon to avoid any repercussions on there.
Of course this is all speculations we've been entertaining ourselves with this morning.