Even if this were true, (which it isn't due to the vast difference between Sagittarius A and the galaxy as a whole. Remove Sag A, and the galaxy would hardly notice it), your claim of a difference in weight for objects on the leading and trailing sides of the Earth is wrong.
In this statement:
The key phrase is "abruptly starts going fast". You feel pulled back due to the fact that the car is changing velocity in that direction. Once you reach speed, you no longer feel that pull.
The Earth, is not abruptly changing is velocity in the direction it is traveling around the galaxy, it maintains a pretty constant pace. The only acceleration is has with respect to the galaxy center is towards the center. ( if you want to use the car example, it would like when you feel pushed to the side when you go around a sharp corner at speed.)
But even then, the magnitude of that acceleration depends not only on the velocity, but the degree of "bend" in the curve. Even with the high speed that the solar system travels with respect to the center of the galaxy, the curve is so gentle, that the acceleration only works out to 0.000000000018 g (For a 175 lb person, this would result in a difference of 0.000000005 ounces).
And even then, the other key word is "orbiting"
Objects in orbit are in a free fall path. they may be accelerating but all parts are accelerating equally in response to gravity, so they feel no net difference between their individual parts ( other than that due to the early mentioned tidal force). So even that small acceleration in the above paragraph isn't felt. ( a falling elevator is constantly accelerating downward, but someone in it would not be pined against the ceiling, but would just float around like they were weightless)