Definitely fixable in my opinion. I'm not a composites expert, but have done my fair share of 'glassing. Here's how I'd tackle it (based on what I can tell from the pics), but I do mostly wave jumping and stupid hood tricks, no backies or stabs...
- remove any and all loose / delaminated stuff
- drill out the ends of the cracks so they can't spread further
- grind down the edges of the cracks on a taper from each side, so if looking down the crack it would look like 2 knife blades facing each other.
- clean the fresh bonding surface and surrounding area.
- in the "tapered well" you just made, slowly build up the layers to fill in back up to the original thickness. A narrow strip first layed on the crack, and slowly getting wider as you build up and end up overlapping out onto the original non-tapered surface with a layer or two. The tapered area you made before gives you a lot more fresh surface area to bond to.
- make sure to use the right materials...I think for that area you'd want to use epoxy resin (not polyester) and your choice of cloths.
I did something similar on my '93 SN...A 2" nick in the lower hull, halfway up and halfway back, decided to crack. It immediately ran up 5 inches or so to the bondline bend and then 22" forward from there. I did as described above (on the outside) and then reinforced with one more layer on the inside. After 3 years of wave jumping in Lake Ontario it's still holding great.