I hope you don’t have an old Ford Model T running down the interstate!
Sadly, technology has moved on and while I too loved my titanium MacBook Pro when I had one, todays world requires more aggressive protection and web standards have also moved forward so if you get your system running again its not safe connecting to any network!
The CPU is limited other than a word processor or simple drawing database tasks it’s just not powerful enough for even for simple gaming.
So consider that if it’s worth fixing given its limitations, and the cost and availability of parts.
To start with your systems PRAM battery needs replacing as it’s loosing its settings (corrupted). [guide|462] and clearly you need a new main battery as well.
Try to find a used 2011/12 15” MacBook Pro as these run a lot less than newer systems and still run most of the newer OS’s & Apps.