Cristina Dracea, MD, FACS

Unfortunately, you don't seem to have a lot of breast tissue to hide the implant, which means that by placing the implants over the muscle, they will be more visible and palpable (unless that is something that you want). Also, implants over the muscle have been shown to be associated with higher rupture and capsular contracture rates in the long term. Moreover, the larger the implant, more sagging will happen and quicker. I think placing a slightly smaller implant (ie 385-415cc) under the muscle with a small lift will give you a better and longer lasting result.

The answer to your question is Yes, When we repair the diastasis, the recti muscles are brought back to the midline or center, thus restoring the normal anatomical alignment or position which maximizes their function and strength. So, you should have increased strength of your core after the repair.

Having a breast lift will get your breasts to be perkier and round again as you desire. However, you'll still probably lack upper pole fullness, meaning fullness at the top part of the breasts. So, a small implant or fat grafting are good options for that as you are thinking. From the pictures you posted, you look thin so you might not have a lot of fat to give for grafting (even though I can't be completely sure without evaluating the abdomen or thighs). Also, not all of the fat grafted will take (aka survive) so might need several procedures to get you the desired fullness. The fat that does take will become a part of you, meaning the volume will decrease if you loose weight or increase if you gain weight. A small implant maintains it's size and shape, but there are also some implant associated issues that can occur down the line which is a whole other discussion.
In your case, I think you should definitely first be evaluated by a plastic surgeon to see if you're even a candidate for fat grafting, because if you are not, then an implant would be your only option.

What you could do is fat transfer to your indent. You will only need 5 days to recover, it can be done under local anesthesia. Procedure takes about 40 minutes.

The volume of the implant does not change even if you place it subglandular or submuscular. A 245cc implant will remain a 245cc implant. The implant might be slightly flattened initially in a submuscular plane until the muscle relaxes and stretches on top of the implant, but the size of the implant will always remain the same (unless the implant ruptures)