How to edit VanitySearch by JLP to search in puzzle 71 space (not from 1)?

Anybody gone into c/c++ in this project?

Try JLP VanitySearch forked by @allinbit and @Ilker, starting from ranges what you want.
https://github.com/ilkerccom/VanitySearch

It hangs when given keyspace option.

There was need to modify the code. Works fine now.

No need modify, just change some line on makefile to matching with GPU type and CUDA version.

No, there are obvious bugs in the code, like using scanf istead of sscanf.