No. You don't need to make the resistor bigger if you keep the same ratios previously stated.

Yes. IMSWO by looking at the datasheet if you're using a TTL input 2.5 V is above the level supposed to be recognized as a high. Why you don't design it for more voltage than that is curious. I'm assuming you'll have a 12v signal you'll have to schmooze so why not make it 5ish volts and not worry about ambiguity. According the datasheet, if I understand it right, with a Schmitt trigger input 2.5 v is way over a recognizable high. So pick a pin type and design for it.