I suspect that it's two different problems. The fuel accumulator is still the most likely cause of the hot starting issue, but I'd still check the distributor cap and rotor first.
You've already covered two likely causes of the stalling issue. The fuel pump relay and the OVP. I'd clean out the idle valve with carb cleaner and check the condition of the breather hoses. Those hoses are pretty inexpensive, so if you see anything wrong with one, just replace it. Shouldn't take very long either. Check vacuum lines for obvious problems.
Do a search on stalling and see what else comes up.
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino