Just ran the numbers on my battles.
Battle on my eastern flank (4 destroyers vs. 17 subspacers) should be an easy win: I have 136/34, he has 36/12.
Battle on my western flank (2 destroyers, 1 blackbird vs. 9 frigates, 2 cruisers) may be a bit more difficult due to the blackbird's huge defense, but is still a handy 82/26 vs. 16/16.
My western flank may be a wee bit more difficult given that I redirected 4 or 5 smaller fleets to my defense, so they may not all land at the same time. But I have some reinforcements arriving from one of my colonies in my homeworld, so I shouldn't lose my home even if my fleets don't arrive on time. Then they'll come from behind and crush him.
Looks like he was just sending a military probe so far. Maybe battlecruisers are lingering out in space somewhere, but the initial fight shouldn't be an issue.