The answer to the first question is 'decrease/decrease'. As the fuel burns off weight reduces. The reduction in weight reduces the lift required, which reduces lift dependent or induced drag. A reduction in induced drag lowers the 'left hand' side of the drag curve and reduces the value of minimum drag speed. Best range speed is a multiple of min drag speed so if one goes down so does the other.
Most tubeless tyres are radials, like modern car tyres. I think you can get tubeless crossplys as well, though. There have been a few dodgy questions on tyres, this might be one of them.
With a resistive firewire resistance decreases as temperature increases.