I don't see why not. Mine's been out for a week already and looks fantastic.

Yes I guess so but what have you in them? Some plants will not tolerate less than 5C and that is quite often. perhaps fleece most cool nights until mid may.

You'll probably get away with it, but it is a risk - if one of the plants in there is Impatiens (busy lizzie) they are extremely cold sensitive,so those are best brought in overnight. Summer bedding in the UK shouldn't really go out till end of May, though where you are, mid May is usually fine.

For me the wind is more of a problem than anything. We get those violent spring storms. You may need to stake your plants esp if you have pelargoniums like I do, or anything brittle like bacopa, like I do. Mine are recovering nicely but took a hit the day I put them out.

Would bubble wrap be better? More insulation but sunlight can still get through to warm the soil

One thing with hanging baskets is if a frost is forecast you can always take it down and put on a pot in the garage or somewhere sheltered and hang back out again in the morning or when the temperature is back again.