In answer to Question 1, yes that's how it is at the moment. You can use your imagination to generate a reason for why it happens, as in maybe it cleared up later in the day for instance. If it frustrates you, there is a crude but effective workaround to prevent those casualties from occurring:
Firstly, select in workshop settings 'Bad Weather Cancels Flights: Optional - User Decides in Campaign'. This way when one of those cancelled flight days comes up you'll get a message asking if you want to fly anyway. When prompted by one of these, select yes and proceed to the briefing room. The idea is to load into the mission/virtual world and then simply quit out. There's no penalty that I'm aware of for not flying the mission, and then you can automatically advance to the next day (depending on the mission frequency for that day) without any random mission outcomes being generated. No one flies, no one dies.
The side effects of this are that the number of missions 'flown' by each pilot loading into the field increase by 1, and each will receive a small contribution of campaign points counting towards their next promotion. No big deal really, and you could use the mission editor to limit the flight to just yourself if you wanted to.
Regarding Question 2 this has been my experience often also. I've come to believe that every target is different, and that the 'sweet spot' for where you need to be varies. Some locations are quite forgiving in this regard whereas others can be very difficult to attain a good result from. I found sometimes keeping some actual notes of what works and what doesn't with each location can help, if you wanted to go to that extent. I don't use the TAC as I tend to get poor results with it for the location. I'll use the map to get generally on course for the target and then use the F11 camera/bombsight view for photo recon, or F4 view adjusted to look straight down for radio transmissions and note taking. Zooming in from these views, it's possible to see the 3D rendered model trenches of the actual target - they appear as tiny dashes on the terrain texture. With a lot of practice and careful lining up on approach, I try to get myself bang over the top center of these and hope for the best. The best approach incidentally is perpendicular to the front lines. Once you've taken your shot etc, it's best to turn back towards your own lines for safety and then line up for another approach. Many missions will always be duds though for various reasons, such is life.
Additionally, I'll unashamedly admit that I use trims to attain straight and level flight for this purpose, and to ease any small changes in course needed. With exception to rare cases such as the B.E.2, it's unreasonable to expect to have do the job of both pilot and observer without some artificial assistance.
The good news about flying recon careers I've come to learn, by way of following my pilot's stats in the mission editor, is that the game is very generous in awarding points towards promotions from successful sorties. A good result in a two-seater can often be more lucrative in this regard than a confirmed victory flying a scout. You also have potentially more opportunities to make this kind of progress than if flying a single-seater.
