first Half & low energy (2 parts)

Hi! This is a two part post :)

1. I’ve been thinking about training for my first half marathon! I’d love to do a NYRR race (or another that’s hype, cheering crowd, etc) for the vibes, but I’m really confused on how to actually get into one. The 4/6 seems really circular- for example, if you want to do the NYC half, a qualifying 4/6 is RBC Half, which also requires the 4/6 to register 🤨… any tips?

2. I’ve been an on&off runner for about 4 years, usually during the spring/fall good weather. A year or two ago I was at my peak, running 10k , ~9-10min/mile for an average run 1-2 x per week. I even did my first (& only) 10 mile run during that time. I didn’t run for the first half of this year and got back into it in August. I’ve been trying to run at least 1-2x per week, usually 3-6 miles. I’ve been having trouble getting back to my previous speed- I feel like I’m stuck at a 10:30 pace or slower. The past few weeks I’ve been feeling really low energy as well. It’s pretty frustrating considering that I’ve been putting in a decent amount of time and I’m not seeing a lot of improvement.
I’m going to try to vary my runs more (incorporate some short “fast” runs and run slow on my long runs)
Do you have any other tips for how to improve my speed & energy?

Thanks so much!