Regards de-bonding rails. Use something to act as a heat sink either side of the fishplate joint (mini clamping pliers) to protect the plasic sleepers and re-apply a powerful soldering tool to the fishplate joint to release it, then clean up. Or you could cut the rail insitu just behind the fishplate using a fine hacksaw or small "Dremel" type cut-off wheel.
Relaying, lots of methods. I have my trackbed at ground level and use the "floating" method of laying the track directly on the balast and "pining" straight to the earth every metre or so with 10/15cm nails. All rail/fishplate joints are treated with LGB graphite paste, or similar, to protect against corrosion to ensure long term electrical conductivity. I use rail clamps, Hillman, as my track is on an incline and can get "hammered" apart by large locos. The clamps also help to ensure long term electrical conductivity and maintain the integrity of the track formation. Possibly the Peco system is too light for this method and I am not sure about rail-clamp availability for Peco. I use LGB code 332 rail.
My track has been laid this way for 8 years, allowing easy layout modifications, with only minimal maintainance requirements and no electrical problems. Temperatures here + 30C /-12C. Lots of other sugestions will be along shortly

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Max