How many tabs do you have open? I have quite a few and it can cause battery to drop a lot. It also occasionally starts using a lot of battery in the background for no apparent reason, which is fixed by just force-quitting the app.
It could also just be that Firefox is inherently more energy intensive than a Lemmy client. Browsers have to handle a lot of stuff to render web pages, while clients for sites just have to send some API calls. I might try using another browser for a few days and see if the battery usage is comparable to Firefox.
How long did you wait for it to forward? Dread has been under DDOS siege for years straight, so they have to implement just about the most restrictive mitigation measures possible. These unfortunately mean long wait times.