Mabybe this has changed recently but sleeping bag ratings seem lower than you would actually want to go in that bag. I bought a 25 below LL Bean bag after freezing in mid september at 8000 ft. in Wyoming. I've used it in fairly warm temperatures and it's fine. Actually got cold in it or close at times. Not sure if it would do the job in 25 below. To be fair, it is down and I've washed it so maybe the loft isn't what it should be, but i think it's fine.

Another time we got up at 3 in the morning and left because we got cold in 0 degree bags. Was cold out but I don't think it was 0. Not sure if we used a pad, though. So from what you're saying, unless the ratings have changed, I'd say get a 0 degree bag . A lot of places get below freezing in the summer, and this will give you a bit of room, temperature wise.

Haven't really tested it that I can remember, but have heard that for maximum warmth sleep naked. I don't want to do that, so I try to wear minimal clothing.