Idea to fill the tile gap after removing the wall
I think I have another solution, but it's not great.

Remove the entire row of tiles that affects most of the right hand void.
Retile the area on the left, continuing the pattern from above.  You will need to seriously think this through, and maybe intentionally mis-align the tiles a little bit so that the black line on the photo is eyeball straight (Although the void from the removed row will probably be different widths at either end.
Retile the removed row with a small, somewhat random shaped mosaic, making a transition strip between the two rooms.

Like I said before, this depends on finding matching tiles, and also finding an acceptable mosaic.
Get a chalk line, and draw it out on the existing tile before you do anything!