Best glide speed in the 737 is the driftdown speed which will vary with weight (anywhere from about 210 to 250kts near MTOW).
Spot on. From the manual for 737-800SFP
70T= 247
65T = 238
60T = 229
55 T = 219
50T = 209
I’ve played with it in the sim, it appears to be accurate.