Power supply

Assuming you are talking about the Lionchief DC wall pack supplies.

Yes, I've done it myself, yes, since it's DC and polarity is fixed by the track and stardardized plug in system they should not fight each other.

In general, on any layout, multiple feeds is recommended rather than hoping, praying that every track joint is perfect. Not to mention, we already know you have insulated rail sections, so right there is a section that if any joint is loose or not making great connection could be a dead section of track.

A note about DC power in general.

DC packs are fine for starting and staying with Lionchief. However, as you progress in this hobby, there are a whole bunch of items that cannot be run on DC and can be damaged by it. Examples are older items with curlers controlled by TRIACs, some sound cars that have railsounds3, engines that use TRIACs in the motor driver section. Other examples like the vibrating motor powered search light cars- well they don't work on DC.

As you move up, again, you'll want to likely move to variable AC power for track and possibly multiple power feeds.

Try feeding in the center of the dogbone. TWO feeds from the same power supply to each side of the dogbone at the narrow part. This should shorten the length of power feed in the ends of the dogbone and hopefully minimize voltage drop.

Not necessarily. The power supply you are using probably has enough power for your layout.

What can be more important is that you spread or distribute the power from your power supply around the track, rather than just one connection point/feed, so that your trains do not lose power or slow down at locations far away from your one central connection point.

One way you can accomplish this is to connect your power supply output to a terminal or distribution block, rather than the track, and then run multiple connections from the block to various locations around your layout.

One example of a distribution block is shown below.

You can also run what are known as "bus wires" under your layout from the power supply and then connect feeder wires from the bus wires up to the track at various locations around your layout.