Which does make me wonder why the heck the Ancients designed the Stargate to disassemble stuff that enters the puddle in a situation where it's got nowhere to send it.

What situation are you thinking of? The gate can't open at all if the exit can't open. If it can open, there's the big swoosh that blows several meters ahead and disintegrates anything in the way. If you mean the iris, it's set something like a few microns ahead of the surface, so atoms can pass, they just get smashed on the iris. It's not like the gate is going to constantly measure the size of shit that goes through and visually check if someone didn't just put up a wall in front. Also, the Ancients themselves did use shield technology that exact same way, see the Atlantis version, so it is all on purpose.

There seems to be a directional force on things, like a current. Shown most dramatically on Universe's opening, being that such a long trip gave a lot of push. So I'm guessing if you tried to stick your hand back into it, the field would push back.

And it would need that push, because what if something just rolled into a gate gently. Can't have that get stuck, so it's like an automatic clearing effect of the wormhole.

Remember the one Atlantis one where the puddle jumper gets stuck. They have to give enough of a push to get the rest of it moving into the gate, but it came out a bit faster than that push was.

The series is far better, but that's not fair to the movie since it had a unique idea to try and piece together in one shot. The series corrected some of the issues and ran with it, and because it could developed the characters and stories better. And still gave numerous credits and nods to the film that started it all.

It's okay to not like the movie that much, there's a lot of things wrong with it. But more that's right. :)

Yeah, whole knows what kind of scary physics is going on with that pretty splash and whirlpool as the gate manages to fight for stability.