You can't mod credits online, they will just revert back to what they was before. You can boost your credits though, if you can find someone to help. I'm sure there was a guy asking for help boosting yesterday... Check around for his post?
Yeah that's right 1,000 a day, if you wait for a long time you can do more at once, Eg, if you haven't played in 100 days, then you can do 100K credits.
You can boost credits via UNI: Sword Base with the locator. Then set custom challenges to get 25,000 credits per 6 minutes. But you need to be able to mod your save with Liberty Mod Tool. Its an easy 200k credits under an hours time. Pm me if you want the link to the tutorial to mod the save + set up the challenges.