Not gonna get you anywhere I'm afraid. Even at 8k per month you're not anything close to lower Sukhumvit. At the extremes of the BTS like Bearing/Udom Suk maybe, but they won't be the newest buildings.
You need around 10-12k for something decent in the on nut area.
Why take anti-biotics just in case? Take them only if you have something!!! Anti biotic resistance is taking off due to overprescription of antibiotics for "general purposes"...
If you are going out, make sure you have your phones/wallets enclosed in some sort of waterproof bag/case/cover and also try not to swallow the water as the water used may not be even tap quality...
Enjoy your holiday and don't penny pinch. Sure the fx rate may have moved unfavourably, but unless its fallen off a cliff (i.e. >20%), don't let that stop you from doing what you normally would.