Savegame compatibility was broken in r5744. No way around that, your savegame will be compatible up to r5743.

Surgery drains the medkit alot very fast. That is normal.

1): Which items exactly?
2): That is normal.
3): A few heavy guns, like LMGs, have the new 'heavy' tag - you will lose stamina fast when aiming with these while standing. Look for Sandro's recent thread about that, it should mention the corect option to switch it off.