How can I mix methylene chloride, methanol and hydrofluric acid to make a paint stripper?
It is not clear how reliable the concentrations given in the SDS are. It is not uncommon to give a range, but actually manufacture product at one end of the range.
I would take 25 parts of methanol and 70 parts of dichloromethane and add hydrofluoric acid till it becomes cloudy - then back off (add some more CH$_3$OH + CH$_2$Cl$_2$). You may be able to add 4.6 parts of hydrofluoric acid (round up to 5 for the SDS).
The solubility of dichloromethane in water is 1.60% at 20$^o$C and the solubility of water in dichloromethane is 0.24% at 20$^o$C. Ref 1  The solubility of dichloromethane in water increases as the temperature decreases. Ref 2
One unknown is the concentration of hydrofluoric acid and whether higher concentrations of HF are more easily dissolved in this mixture than lower concentrations. The SDS may not give you useful information, but I suggest trying to use the most concentrated HF available - you can always dilute it, and H$_2$O is no friend of this combination.
Methanol and water (and thus, probably also hydrofluoric acid) are miscible and so are methanol and dichloromethane. A recent question on StackExchange (Ref 3) gave a ternary diagram of water-methanol-dichloromethane:

The line separating the one-phase (M) from the two-phase regions (I) does not go all the way to the top, but you can see that there are homogeneous mixtures with a lot of water, methanol and dichloromethane.
The Safety Data Sheet is required to list hazardous ingredients, but not non-hazardous materials. Some stabilizer might be added, hidden in the 15% range of dichloromethane and 10% range of methanol, that could keep the mixture homogeneous. One compound that comes to mind is propylene glycol. If the commercial product is cloudy, it might be stabilized with a thickener like guar or xanthan gum. Wax has been used as an evaporation inhibitor in paint removers containing dichloromethane; it might also act as a thickener and stabilizer.
Ref 1. https://macro.lsu.edu/HowTo/solvents/Dichloromethane.htm
Ref 2. https://en.wikipedia.org/wiki/Dichloromethane
Ref 3. Mixture of water, methanol and dichloromethane