There are lots of ways to generate the checksum. Google can help you if you want a program to do it, there was one or 2 posted on this thread, packageIO can do and you can even do it in hex workshop with the Custom CRC32 option which is how I've been editing my save.
The way the saves are laid out is almost the same system ME2 used so its pretty simple to hex edit whatever you want/need. As for the health upgrades it looks like you will need a save with an upgrade applied that was acquired at a research terminal not as bonus from levelling up.









