Nice reading, and great pictures. My son has basically the same bike in Malaysia, his is a Nitro 150, but they are also sold under other names. Mecanically (engine) has been good, no problems at all. Starting when hot got the be a problem, but that was cured with a new spark plug. Quality of componants and the metal used is very bad compaired with Japanese bikes, and we faced some problems getting spare cycle parts as nobody carries spares for these bikes. Luckily bodging bits off other bikes works OK. Chain is elastic as you say, but ofter 6000km its still going OK. Another big issue was punctures, we found that unless the tires were inflated to 40psi and checked regularly, the tire was actually moving on the rim and stressing the inner tube. Getting imported heavy duty scrambles inner tubes and keeping the pressures up seem to have cured this.
Best of luck.
"don't wait for your boat to come in... swim out and meet the bloody thing"