Add these variables to the S_PlayerSave struct found in the other folder in the blueprints folder.
Add the highlighted nodes shown below by dragging out from the player inventory component and searching for them. (If you do not have the variable in the search then you need to follow the DIY Guides to add the max variables to your project if you are not using an updated version from the launcher)
Create the Events shown below and set them to Run on owning client with reliable ticked. Then have there outputs set the max stats.
Next add the nodes shown below to the load save game after the Client Update Weapon Inventory node.