1. I am getting a temp reading of about 78-79 in the evening...it was warmer at around 84 a few hours ago in the afternoon. Humidity at 48%-50%. Should I try to increase these numbers? To what and how?
Is this your hotside temperature? If so it is far too low. It should be around 92*F. I see that your probe is placed under the lamp (at least, I think that is your probe). Move it to right above the UTH (right on the glass under the substrate). You should not have a significant night drop in temps, they should be consistent 24/7. Humidity is fine
2. Do I run both the light and the heat pad 24/7?
If you need them both to keep propor temps, then yes.
3. The water dish takes a lot of space - can i get away with a smaller one? I keep seeing these small water dishes in videos - mine is huge.
Yeah you can use a smaller one. Some people say you need a bowl big enough for them to soak in but the only reason they soak (usually) is because they have mites, and that is a problem.
4. Is the 75w bulb positioned correctly - do i need to change it?
You have it on the right side (the cool side) but I think the wattage is a bit high. This lamp should be used to bring your ambient temperatures to around 80-82*F