1. yep, just take a taxi, around THB 250-300.
2. anywhere close to the Sky train (aka BTS).
I use WOTIF.com a lot. For USD50 there are many places on Sukhumvit Road, which are also neaer teh BTS. The link below is a search for places <USD100 (or THB 3000) in Sukhumvit area.
http://www.wotif.com/search/Advanced...2&viewType=all
The 'mystery' hotels can be very good value, once you google around to work out which ones they are. For example, I can recommend the following for your budget:
I reckon the 4.5* hotel for THB 1910 (US63) is the Dream, usually around USD100
Friends have recommended the 3* Darjelling Boutique for THB 1150
I can recommend the City Lodge on Soi 19 solid 3.5* for THB 1500.
3. Well, it IS the hottest part of the year. But still, get out and about! Shop in aircon 1100-1500, or sightsee 0800-1200. Nap, until 1700, then head out for a cool beer (or whatever) and then enjoy the evening.......
I arrive on 7th, so will miss. PM me if you have any questions.
Cheers, TK