For completeness, have you tried a different ethernet cable, or a known good one, or verified you aren't accidentally using a crossover cable (all things I've done in the past)...
Also without a customized/updated ROM that skips the RAM check, the time-to-splash screen can be several minutes with a gray screen and a responsive cursor. The RAM check was designed when 8MB was the standard max and the 64MB check can be a lot longer.
You may need a IIsi or 32bit clean ROM for your SE/30 for it to use those SIMMs. Also, SE/30s are very picky about banking and mixing (trying them in a different bank and/or removing other SIMMs you might have in there may help). I've used these 4 x 16MB PurpleRAM successfully in an SE/30 with...
30pf "should" be close enough. Should. If the 30pf crystal does not work, or does not work reliably, you can try soldering a 3pf non-polarized capacitor between the pins of the 30pf crystal. This would effectively create a 33pf crystal.
The SE and SE/30 have a metallic spray paint on the interior of the computer housing that acts as shielding. IIRC the Classic and Classic do not in order to save costs, and I believe the FCC regulations changed over time allowing them to move most of the shielding to the chassis.
There are some...
The case cracker is harder to find these days. You WILL need a long shaft Torx T15 screwdriver to remove the screws under the handle (at least 15cm long) And I have found that a set of plastic spudgers is gentle enough to loosen the plastic around the case so you can pull the back half off...