Hello, I can help give you input as a UK citizen who married a US Spouse and was recently visa approved this month.
1.) I saw others stating the same thing about including relationship evidence, but not once did I include anything on my I-130, DS-260, and not even at my embassy interview in London was I asked for any relationship evidence. I was simply asked basic questions such as how did we meet, where did we first meet, my partner's job, where we got married... I had an envelope of pictures of us together and not once was I asked for it.
Myself and my partner actually lived together for 4.5 years in a flat/apartment, and I had evidence as such to this but other than verbally offering it, again, they didn't ask for any physical proof whatsoever. This includes financial where we didn't have shared accounts as my OH was temporarily over in the UK studying on a student visa, so we had no proof of shared income or anything. (I paid our rent and bills from my UK bank account only.) I was still approved. I hope this helps put you at ease, but also remember each case is different.
2.) I can't answer this one in detail but I believe if you have a marriage certificate to include on the I-130, that's about as much proof as I needed and perhaps that will be the same for you. Still, better safe than sorry - some pictures can't hurt.
Be as prepared as possible. I wasn't asked for any physical evidence apart from uploading what the forms asked of me. My interview was all verbal affirmations. Nothing additional in terms of photos, shared financial records etc was asked. I hope this helps, and good luck!