Plotting money market equilibrium for 2020
The graph is almost correct given the assumptions about what is happening but not quite. The proper graph should look more like this picture I made in LaTex using tikz:

Where $^*$ denote the new state of things given your assumptions.
You are right that money demand shifts to the left and money supply to the right, but your graph missed an important fact that money demand at zero lower bound (ZLB) becomes flat. This is one of the reasons why monetary policy looses its potency around ZLB (see Blanchard et al. Macroeconomics a Eurpean Perspective pp. 96).
Correction of some misconceptions:
In your post you also have some misconceptions let me correct them:

This is the tricky part, as money demand is not something we can directly observe in practice, though I tried my best to be objective/conservative.

We actually can observe money demand at a given point in time (only the whole demand function is not directly observable). Furthermore, we actually even can, using econometric methods, properly estimate the money demand function.  See Jawadi &amp; Sousa (2013) or Narayan, Narayan,  &amp; Mishra (2009), for examples of that. However, of course this cannot be done in real time but only retroactively as we collect enough data about given time period, so to do that for period covering entire COVID19 crisis this won't be possible until few years down the road.

helicopter money offsets deflationary forces

central banks are definitely trying to expand money supply right now but not via helicopter money. Helicopter money means central bank is directly sending money to households. This has not yet happen to my best knowledge (at least not in US, EU or UK), although there are economists calling for central banks to do so (like Gali 2020 in his VOX$^{EU}$CEPR post).