Well, if you have decent endurance, you're not going to see a lot of gains in that area in a month. I have two recommendations.

First, intervals are a pretty good simulation for what you experience in a paceline. Make sure you are well rested before hand - the better you are rested, the more benefit you get from doing intervals.

Second, some tempo rides can also help. You do a ride right at your LT but only for 20-30 minutes.

Both of those should help.

I don't think much of your idea of trying to do both intervals and long rides. You need training specificity rather than big long general efforts.

You might also consider some hill repeats or over/under intervals.