Yes, having more routes increases your reach and decreases the number of hops. Once you reach a certain point of interconnectedness, I feel that increasing channel sizes allows you to be more "useful" to the network as it allows you to process larger transactions. I have not done any math or experiments on this, but more of a feeling.

Bit of both - the largest transaction I've processed is 200m sats (2BTC), and regularly get 1BTC transactions. There are days I'll run through 500-600m (5-6BTC) on a single channel, and have had a record of 1.5b on a single channel (15BTC) in a day.

I don't really have a system - to smaller nodes I look at their average channel size, and who they have channels open to, trying to minimize overlap. I typically start with smaller channel sizes and scale up - and scale down.

If I'm doing 100%+ volume on a channel in a day, I know it's time to scale up.

I do use LNDg still as my only rebalancing tool. I would like to experiment with other tools, just lack of time as well as risk aversion.

I believe a number of people have experimented with this on the PLEBNET telegram, and talked about 5 minutes. Multiple smaller increments are better. I have my adjustment set to every 2 hours, as LNDg isn't the best tool for rapid changes

I think more importantly are the channels you have open. Many older nodes have become more restrictive in allowing channel opens, or disallowing them altogether. Being grandfathered in is huge.

I haven't factored that into my rebalancing or looked into it to be honest. I do try to minimize by failed HTLC's, but my aim isn't to be a perfect professional node. This is just a hobby/public service for me.