I'm away from my machine with AI War on it at the moment so I can't look at the save, but I'll offer a different perspective from what I can glean from the posts in case you change your mind and decide to try salvaging the game.
One word of warning -- I play with very high auto-AIP (1 per 5 minutes) so my advice is geared towards killing problems *fast* and betting you can beat the clock before the AIP you're racking up kills you.
AIP~300AIP doesn't sound fatal to me, unless maybe you are playing on a very high difficulty? If it's 8 or less, you can turn this around with enough aggression I bet, unless you have been dealt an incredibly unlucky hand with unlocks from ARS/fabs. The low-AIP ship has sailed, but moderate-to-high is still taking passengers.
Definitely splat those remaining AIP reducers ASAP with your Raidstars since it sounds like you are feeling pinched, it sounds like that will bring you back down under 300 again and give you some breathing room.
DefenseReposition turrets etc on your worlds to a maximum efficiency layout (i.e. Kahuna-style) -- if you have the K and haven't unlocked them yet, Area Mines are godlike, especially when placed in packed lines. I've seen packed rows of 3x10 Area Mines instagib hundreds of ships. Sounds like you have Spider turrets so if you don't have Widow Mines already, you may be better off putting spare K elsewhere since you have a source of engine damage. If you don't have them, Grav turrets of at least Mk.II are also godly. If the ships can't reach you, they can't kill you, and even if you have weak turrets they have more time to rip up the incoming trouble.
Speaking of turrets, if you don't have them already, grab the Core controllers for Missile, Laser, Needler, and Sniper if you can. If you are over 300AIP, you should have plenty of HAP so you don't have to take and hold the planets if they don't get you closer to Black.
To give you an idea of how insanely effective Mk.V turrets are, Mk.V of those 4 mixed in with Mk.I Lightning, Mk.I Tractor, Mk.I HBC on certain planets, and Mk.I-II Grav, plus some mines, was enough to hold off virtually all waves without fleet assistance up until around AIP 500 in a recent difficulty 8/8 game. Those were Assassin and Sledgehammer waves too, so bigger than normal. Grav III + Needler II with some targeted warhead assistance (is that a Carrier on my planet or a flying bullseye?) held the line through AIP 700. Planets with a Botnet on hand held until final victory at AIP 936.
TL;DR: Grav III, Area Mines, and Core turrets are amazing. When in doubt, just apply Mk.I Lightning warheads to offending carriers until the problem goes away.
A somewhat risky strategy that can work under the right circumstances is, if something has pushed/will push through your lines, and it's not EMP immune, and you have enough Mk.V turrets to kill it before the EMP wears off and it finishes off your command station, is to EMP your own planet. Mk.V turrets are EMP immune and will be able to fire freely.
ThreatSame deal for Threat -- when it finally picks a planet to stage an attack for, watch for it to ball up as it prepares to move in, but is still waiting for the last ships to join. Once it does that, you have several options for rapidly destroying it, depending on your fleet strength, tolerance for more AIP, and how scary the planet is it's staging on. If you have a Tachyon-free path, you can just sneak a Lightning warhead up to the ball and fry it. The Missile frigates will be about the only thing that's left, and they won't be willing to attack on their own. If that's not an option and it's too dangerous to just sic your fleet on it, EMP them first, then maul them while they're locked down. Watch out for the Starships though.
If you have some flavor of reclamation available to you, hunting Threat can be a nice opportunity to boost your own fleet.
Core Worlds/Homeworlds
Otherwise, I'm not overly worried about that Core world by Red being on alert and unneutered, assuming you have Assault Transports or a lot of Cloaker starships. I have yet to bother neutering a Core world even on alert, well unless you count nuking one that had become a staging ground for 80,000 strength of Special Forces. <cough> Just hit and run the Tach posts to clear a path, and shoot/Sabotage down the Warhead Interceptor if you are open to using warheads on the homeworld. After that, it doesn't really matter what's on that planet, you're going to just sneak thought it and blow up the homeworld on the other side.
Black being so many jumps away is a pain, but can be dealt with. At 9 hops, you only need to pick two planets to get you in range and avoid deepstrike, and you don't need to hold both permanently -- deepstrike only counts 4 *AI* controlled worlds in a row. If no one controls it, it breaks the chain and it has to start counting from the neutral planet.
Just hop your way to a good staging planet and prep that one with defenses to deal with the Threat backlash/Exos, and kit it out with all the constructors or warp gates you need to get your reinforcements in place. I would recommend getting a world adjacent to the Core world, but if you have to strike from farther, it can be done. I've staged HW assaults from the max 4 out and won, but it's a pain in the arse to move cloaked warheads that far and your Transports will be in sorry shape by the time they reach the HW. But it's not impossible.
As for the Homeworlds themselves, I would scout both before choosing which one to attack first. You already have one Core world on alert, so unless Red's HW is significantly more dangerous than Black's, I would probably kill Red first. I prefer to kill the easier one first in case I need (want) to go crazy with the warheads on the last world, so I don't have to worry about living with the spike in AIP for long.
One last tip on the HWs, since I noticed some comments about them being off on the ends of strings of planets. If you can cut a HW off from the rest of the map by blocking it with a fortified world of your own, you can likely prevent the Special Forces from rushing in to pile on while you attack, leaving you to only worry about the planet's own garrison and the Reserves. Just be careful not to launch the blockade until you're sure the SF are safely away from the HW -- I found out the !!fun!! way last game that if you split the graph and trap the SF on a disconnected chunk of the map, it will convert to Threat after ~20 minutes and the AI will begin spawining a whole new SF somewhere else. You will probably not enjoy the results if that happens.
Hope all/some of that helps if you decide to try to salvage this game after all! And remember, when all else fails, the nuclear option is
always an option...
EDIT: I see Pumpkin updated while I was typing this, ignore anything in mine that's redundant/no longer applies.