I had a '94 5.8L van previously, and had both symptoms. Both are caused by the fuel pump, but actually unrelated except for age...
1) The fuel smell is likely the o-ring that seals the fuel pump to the tank. When this fails, fuel sloshes out at a surprising rate, making that overwhelming gas smell. That said... the next time you park the van, cycle the keys a couple time before starting up, and inspect the frame rail and under the hood, to rule out any leaks in the pressurized side of the system or fuel return line.
2) The vapor lock is pretty much just that, except it's cause by the fuel pump motor running hot, and boiling the fuel internally. This is why hot weather contributes.
Fix for both is simply a new fuel pump. The hyrdolock issue can be reduced by keeping the fuel tank more full, but since you have the o-ring leak, you'll just slosh fuel out faster.
Some parts catalogue will say your fuel pump assembly isn't available. That's partially true. It should refer you to the '97-'08 fuel pump, and then also tell you to buy the adapter for the wiring plug, to allow the newer fuel pump to connect to your wiring harness.
You'll have to drop the tank for the fuel pump swap, and because of the age, might need new hoses (filler and vent). If they looked cracked at all now, go ahead and replace them, because the extra movement from dropping the tank will just worsen the cracking.
2000 E450 dually V10 wagon