Block Size Limit: What is the community's stance on potentially adjusting the block size limit to manage growth? Are there ongoing discussions on this topic?
If you control some large mining pool, then you can shrink it in your own blocks, produced by your pool. But I expect it will be hard to change it on consensus level.
Second-Layer Solutions: How effective are second-layer solutions like the Lightning Network in relieving the main blockchain? Are there experiences or concerns that we can share?
It is good, if you can process N payments off-chain, and then summarize them on-chain, but it is unlikely, that this alone will be sufficient.
Pruning: For those already implementing pruning, how has this impacted your node's resource usage? Any insights or recommendations for others considering this approach?
If you cannot buy a larger disk, then you should apply this now, and put for example 500 GB (or whatever) as your pruning size. But of course, note that by default, your node will send only last 288 blocks (or something around that) to the network, if you use default settings.
Optimizations: Are there any ongoing efforts or developments within the Bitcoin protocol to optimize resource usage and improve scalability?
Yes, UTXO-based model is in progress, you can check "assumeutxo" and similar features.
Here are some current stats as of today:
Because of Ordinals, and other stuff like that, just assume 4 MB per block. It is better to overestimate it, than underestimate, and buy too small disk.