You've gotten a good set of answers so far, but I thought I'd still answer your questions as well for another set of opinions!

Full disclosure, I've owned the logitech g wireless headphones (the top of the line ones) and audio technica ath m50x's and have used a scarlet dac/amp and also have used a schiit modi magni dac amp.

1) No, wireless will not ruin your experience. As the technology gets better, wireless will get even closer to the quality of wired which imo is still better at the moment. Wireless definitely wins on convenience and I have a pair of jaybird x2s I wear 6 days a week to the gym.

2) maybe. Depends completely on the headphones. In my opinion of course, the "surround sound" headphones are bs. They have a lot of small speakers instead of two larger better quality ones and there are a lot of youtube videos on this so I won't elaborate too much. But, some usb headphones offer features that don't typically come with 3.5mm headphones so that can be a plus.

3) depends. I noticed a sound difference, but then again, I sold my dac because it just wasn't worth it for me. If i wanted to, I would put my dispensable income towards it, but I would rather spend the money on just a better pair of headphones.

4) just by itself, not that bad. But I would still recommend just a regular pair of headphones and maybe a modmic or something?

5) in speakers yes, in headphones no.

Lastly, if you might be searching for headphone recommendations, I have the Sennheiser HD8 DJ as my go to heaphones along with the jaybirds for the gym and I couldn't be happier. I think they are some of the best closed back headphones, but I definitely paid a premium for them. I don't plan on buying headphones for the next 3-5 years so it was definitely a good investment for me.

Let me know what you think about my responses and I'll send any follow up you like!