Help diagnosing 2011 CR-V issue

Having some issues with a 2011 CR-V EX-L with about 127,000 miles. If anyone has some insight, I'd be grateful.

• Vehicle runs fine in cool weather and in early mornings when temps are low. I live in South Texas so hot weather is always at hand.

• As weather gets warmer, vehicle has very slow and sluggish acceleration from a stop. As in I fear needing instant acceleration to merge with traffic, navigate an opening, etc.

• It takes a hard goose on the throttle to get it to shift into second, and after that it lingers to pretty high revs before it'll go into a higher gear.

• Gas mileage takes a noticeable hit. If weather isn't too hot I can get around 21 MPG in the city. Plummets to 16 or 17 when it's acting up.

• If I'm in standstill traffic, like in a drive-thru line or (worst of all) picking up kiddos from school, the temp gauge climbs to a few blips away from the top of the scale. Haven't had a noticeable overheat yet, but it's dicey -- especially when you're trapped and can't pull over. And hoo-boy is the acceleration awful when I can finally get moving.

Took it to a dealership once and asked about it. All they did was supposedly upgrade the transmission package or something. I'll avoid that route from now on.

Much obliged for any insight. Thanks.