How does LC50 translate to "real world" exposure for paint thinner?
The $\mathrm{LD_{50}}$ and $\mathrm{LC_{50}}$ (lethal dose and lethal concentration) values are measures for acute toxicity as you noted. Long-term exposure is generally not depicted well by these acute toxicity measures. A.K. pointed out, how improbable it is to have a serious risk of acute poisoning. (Also note that the vapour pressure is given as $2~\mathrm{mmHg}$, which is $2.7~\mathrm{mbar}$ in proper units, meaning that evaporation will be very slow at ambient temperature and pressure.)

Chronic toxicity data is typically given as workplace exposure limits, under the reasoning that if you work with something every day and its concentration is less than the harmfulness limit, it should be okay. Scanning your MSDS, I did not come across any such value, so there should be no serious chronic toxicity if you keep your room well vented and don’t forget to recap the bottle, etc.