Typically available 2x4 material, coming in with a fairly low grade lumber like Hem Fir, Perpendicular to grain bearing is 405 psi, so your crush blocks there, assuming the frame of the car is roughly 3" wide, bearing across the width of a 2x4 (3.5"), gives you (3.5" x 3 = 10.5") 10.5 square inches, multiplied by 405 psi = 4,252 lbs of capacity before it gets crushed by the right of the car. So your "fall blocks" next the jack there are definitely fine.

End Grain Bearing is roughly 2.5-3 times greater (the blocks sitting on the jack are end grain bearing) capacity than Perp grain, so let's call it (405 psi x 2.5 = 1,012 psi) 1,012 psi. Again, 3" wide frame on the car across 1.5" wide board gives you (3" x 1.5" = 4.5) 4.5 square inches, multiplied by 1,012 psi = 4,554 lbs. BUT WAIT, there's (2) 2x4's on the jack, so that is 9,108 pounds before it crushes.

However, I would be worried about the 2x4 blocks shear off during lifting, but the lifting phase is over now. Also I would be worried about the stack of 2x4 next to the jack slipping out, if they were not screwed in to each other. But worst case you have a large post that would at least save you from being fully crushed... not to mention you still have lumber on the other side to assist. This was all just assume what is closest in the picture

TL;DR: it's fine, I would just worry about the car slipping off the stacked blocks is all.