I've never used the SWM lenses so I really can't comment. If Ian is around he'll have more hands on experience with them that I do. I did have a 50-200 f/2.8 (the non-SWM version) on my E-510 and never any problems with "slow" focusing!
The E30 doesn't use the same body as the E-3. The E-3 is magnesium alloy and the E-30 is a glass fibre reinforced pastic. Both are sturdier than the E-620. The E-30 is the closest you're going to get in size and weight to the E-3 (other than having a second E-3!).
DPReview has some good in depth reviews of all the cameras you're looking at (links are
here for the E-3,
here for the E-30 and
here for the E-620)
Compact wise, Olympus do a couple of "tough" compacts but they don't do a waterproof PEN. I remember reading a story that a member of Oly staff rinsed an E-3 under a tap at the official press release when something was spilt on it but it's not something I'd try at home.
Sticking with Olympus, have a look at the
mju Tough 3000 which is new out and around £200 and the
mju Tough 6010 which is a little older and better specced for around £220.