Two stroke oil is alot better than it was, alot of old bikes were calling for high oil mixes but 32:1 for a cast iron cylinder or 50:1 for an aluminum cylinder is about right using conventional nonsynthetic. There are many posts on the subject.
If the condenser is original, it must be bad. You can search for how to mount an external condenser. Replacing the spark plug is the first thing to do because its the cheapest and easiest maintenance item to take care of.
You can use a little bit of Hondabond sealant to seal the carb flange if it is the round vlamping type but you would want to do a leak down test first to find any possible engine air leaks. You can search here how to do it but basically you plug the exhaust port and pressurize the carb port with about 5 psi and look for a pressure drop on the gauge. Brushing on some soapy water will reveal the leaks on tne outside of the engine, but if not found, the crank seals are the usual leak source.