I'm stuck writting a WWII spy-fi thriller

I'm writing a spy-fi thriller set late in WWII, the spot where I'm stuck is this...

A group of German senior officers convene at the summer house of one of them. The big bad proposes overthrowing Hitler since he thinks he's squandering what little they have left, and has a plan for turning the war around in their favor. Some want to hear him out while others put honor before reason.

Meanwhile, our hero, his love interest and two of his men learned of the summit earlier, but not enough to get any backup or proper equitment. The plan to find out what the summit is about and to learn the identity of the big bad who'd been a thorn in the side of the allies, and was known merely by a codename.

The hero manages to sneak into the house, and listens to enough to realize what they're plotting. Upon hearing one of the officers storm off, he signals for his two men to follow said officer.

The officer runs into an ambush set by the big bad for anyone who wouldn't join him, he's wounded, but before they finish him off, the good guys arrive and kill the ambushers. One of them impersonates a German soldier and gets the name of the big bad out of him.

I'm stuck as to what to do next. I want the segment to conclude with the big bad running away and most of the officers dead with perhaps one or two fleeing to report the big bad's plan back to the German high command. I don't know how, though. I thought about the woman being captured and brought to the house, so the hero has to break his cover, but I'd hate to do that.

Thoughts?

Here's an idea. One of the coup plotters is an SS officer. He stands up and announces (with appropriate fanfare) that anyone who doesn't help him arrest the big bad will be executed. Like the good guys, tho, he has no backup, he's bluffing. A gun battle ensues. Whether the SS guy survives depends on whether he can provide intel.

Hey, that's not bad. I could work with that.

A bit more info, the big bad already has a conspiracy in place, he just wants to make sure these particular guy aren't against him when it goes down, he either want them on his side, or under suspicion of treason by the high command, Hitler being very paranoid at this point.

For added confusion, the SS guy is a plant by the big bad. The idea is to confront the henchmen with the the consequences of revolution, that is, if they go forward and lose, they're dead. If they're willing to proceed with that understanding, the chief feels he can count on them. He expects one or two to turn tail, but he gets about one-third of the group (Nazis are basically cowards).

There's no need for the one guy who voluntarily quits (and gets shot). The two grunts will have their hands full with the massive gun battle. The shooting could go on for several minutes, or the turncoats might not get out of the room. Depends on your plot: if people escape one at a time, aren't they more likely to leave the conspiracy? As far as they know, the SS really is on to them.

This is the point of the story where the Big Bad and the Hero have to come face to face. The hero has fucked up the big bad's plans time and time again for years, while the big bad had orchestrated an operation that led to the annihilation of the hero's former nakama and the career death of his mentor, and they haven't even seen each other.

I like your ideas, but what I'm trying to accomplish is to create a confrontation without it seeming forced, that also involves the hero, and allows the big bad to escape.

So how about this?

Hero sneaks into the house, listens to the whole thing. Luftwaffe General demands they arrest the big bad, causing everyone on the fence to pick a side, creating a Mexican stand-off. Big bad explains the situation as a no-win situation to all involved, so he allows the General to leave, without really explaining why but explaining that the General cowardice prevents him from staying there to stop him.

Hero signals the other three to pursue the General, but only his lancer and the big guy do hile the smart chick stays. He doesn't intend for them to do anything useful, he just doesn't want them to be drawn into the unwinnable firefight he's about to start.

The coup seems to be thwarted, but then the other loyalists begin to have a change of heart, partially due to the Luftwaffe General's penchant for career-orientated backstabbing. One by one, they switch sides, and the big bad reveals he has measures in place to stop the General from reporting them.

The hero, who's a teensy bit suicidal, wants revenge and recons his superiors don't want a group of competent General messing up matters when they're so close to victory in Europe, decides to light the powder keg. He walks into the room, pretending to be one of the officers' escorts (everyone assumes he's someone else's) and slips in a bomb, similar to an earlier scene that saw his platoon wiped out. He's rebuked, but not before he's seen the big bad.

The bomb goes off and violent confusion ensues. Through confusion, luck and the intervention of the love interest, everyone is dead, but the bad guy slips away, wounded. The hero and his LI walk out too.

The lancer and the big guy run into the fleeing General's car as his escorts, who had been bribed by the big bad's men during the summit, stop the car to kill their boss. The good guys stop the hit and the lancer, who is a German defector, gets some intel out of the dying General.

Little does the hero know he's accidentally allowed the big bad's real plan to mostly work. The intel retrieved by the lancer and big guy is later doubted by their new CO, due to the nature of the intel as well as their dubious personal histories.

I have no direct advice to give, but your story sounds very interesting. Is the Big Bad Doomed by Canon? Or does his plan succeed?

Doomed by canon.