Can I widen my forehead while reducing its forward projection for a wider and flatter look? (Photo)

It is very hard to comment on your question without good series of photos and in person evaluation. In general, forehead flattening can be achieved shaping anterior forehead with burr; lateral widening can be achieved with silicone or other type of implants. In person consultation with board certified plastic surgeon experienced in this type of surgery is recommended. Good luck.

I think you can approach your concerns from several directions. The temporal aspect that you want widened may not seem as necessary if the anterior hairline were lowered with or without augmentation of the superior anterior forehead  using methylmethacrylate or fat. Though this augmentation is combined many times with burring down a prominent supra-orbital ridge (esp. in facial feminization surgery) I do not sense that you have that issue from these photos. Silastic temporal implants or fat can augment the sides but, as mentioned, may not seem as necessary if the above procedures are done first. Obviously, an in-person consultation or maybe even an online virtual consultation would be better than making recommendations from non-professional photos.

To accomplish your forehead reshaping goals, as you have mentioned, you need to do a combination of side of the forehead widening (temporal line widening) and central forehead flattening. The only way to do so in a reliable manner is with custom made lateral forehead implants (not PMMA bone cement) that create a new temporal line combined with central forehead flattening by bone burring. Computer designing to make these changes, just as you have done in a more limited method by diagrams, is the most accurate way to put these two forehead changes together in an integrated smooth manner.