When I jump in my ships immediately get shredded by energy weapons - there are dozens of hits doing nearly 300 damage EACH!
A fleet composed of ten 120,000 ton close range brawlers with 30 armor layers plus a lot of shields gets instakilled the moment it jumps through the gate. I could of course bring more, but i just dont see it being worth the investment nor time.
120,000 tons is not a large fleet at all, no matter how much armor you put on the ships. Ten 12,000-ton ships are also not very large individually, you will regularly see NPR capital ships in the range of 20k to 25k tons or so. A typical NPR battle fleet will displace 200k to 300k tons in total, and the NPR could easily station multiple fleets at this jump point if you have not already chewed through several of them in a war of maneuver and attrition. I suspect a large part of your problem is that you simply do not have a large enough fleet to do the job. Similarly 200 fighters is at most only 100k tons of easily-destroyed ships, not nearly enough.
Really there is not an alternative offensive strategy here besides "build more ships". Of course you can play defensive while exploring for a new way in, as Andrew suggests, but Aurora is by and large a game about long-term strategic decisions more than brilliant tactical cleverness. Of course there is always some of the latter, but if you come up against a situation where you need ten million tons of ships, or ground units, or etc. that you do not have, usually the only answer is to take the time to build what you need, and the only way you could have "played around it" was to have built these already in anticipation of a future need (and this is not always something which was possible).
I believe you are misreading the OP, it is not a fleet of 10 12,000 ton ships, it is a 1.2 million ton fleet composed of 10 120,000 ton ships.
It is funny how shields come online "instantly" and weapons suffer from "jump sickness"...
One of the ways to do this is to put through a "pod" (or hundred), going to 1 second intervals, once it goes through, "release" the missiles on it (them) have them all two stage, with a decent separation value, and make sure they all have sensors on them, will thin out the awaiting fleet, basically ya dump a minefield on the JP for them to deal with, and then bring the ships in afterwards...