my dear, you experimented correctly. 2 acs may be run on a china gas genset under 10kv but its for a very short time. you cannot use it for daily purposes.
other thing is, if you want to use acs, go for a 15kv genset atleast. you would be better off then.
brigs & straton is a good genset but not a very wise option.
you want cheap solution with longer/safer output. go for locally assembled genset. use a corolla engine or a nissan efi 1.6 engine. total cost will be 1.5lacs and you will be able to use it on gas easily. use 2 acs and all other electrical appliances with ease.
i am runing a company (not a shop) in lahore and we deal in industrial gensets - buy,sale, repair and maintain.
suggesting you the above from experience.
hope it helps