I have just installed a new optimate lead on my battery and the tank was full right to the brim tank was raised up for about half hour to fit and no leaks
If the chain is in good condition just buy new masterlink.i definitely would not ride till its replaced the damage it could do does not bear thinking about if it breaks
Mine where like this when I bought my bike not long ago.i used coca cola and a soft scouring pad to remove surface rust then buffed up with autosol metal polish only took a couple of hours to do