700 (Q50, V35) need to improve verbal

First of all let me congratulate you on your Quant capabilities.
Next, I would urge you to stop doubting yourself regarding improvement in Verbal. The stagnation is pretty much a common story. However, you need to do a root cause analysis regarding your failure to replicate your performance in your standalone tests. Are you timing yourself in the individual tests? are you sure its not a stamina issue?

Dig deep to find why this is happening. Sometimes when switching from one subject area to another (say SC to CR or RC to SC) the brain goes through a slight lag (think in terms of a system hang). If this is the case, then the best way to help yourself is to practice all the 3 sections together. Initially it might not be so good, but eventually it should pick up.