The wall seems to have 'full dimension' studs and the markings of old lath and plaster. I don't see plywood sheathing on the exterior walls. All in all I'm guessing that your house was built prior to WWII and is either 'post and beam' or 'balloon frame' construction, both of which are radically different in terms of structure and loads from modern techniques.
Here are wikipedia links for those techniques:
- post and beam construction
- balloon framing
- platform framing ("typical" modern wood framing)
Can you post some photos that show the original framing for the original windows? I'm guessing the original construction did not include headers above the windows. Also I do not see any indication that jack studs were used in the original construction.
If your house is post and beam, then I don't think there are any significant structural issues.
If your house is balloon framed, this is how I would 'fix' it, with the jacks (red) and cripples (black) going through the floor to bear on what ever the existing old studs bear upon. The header (green) consists of two 2x10s sandwiching two rippings of 1/2" plywood (or whatever).
Based on the current state, achieving this is rather quick and simple. It does not require starting from scratch: the window and existing new 2xs do not need to be removed.