A couple machanic questions (93 190E 2.6)

I have a couple machanical questions. My idle seems a little rough... not really rough, but the idle sounds "bubbly" if that means anything.
When you give it some gas it smooths out ,but it feels like you can feel it firing on each cylinder rather than being smooth at idle. My idle speed is a little over 500 in gear and about 700 in park. What could be causing this?
also, should the idle be higher? If so, where is the adjustment? I see the black adjustment where the throttle cable comes in, but that's ajusting a bunch of linkage with switches that disengage when you titghten up the cable with that adjustment, so I'm thinking you do it with the linkage close to the throttle body.
Also, there's about an inch of play in the gas pedal before it accelerates. The slack is in the linkage I menationed and not the cable itself so I'm guessing this is normal. Is there any way to remove the slack?

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