The zip-tie method should allow you to remove the tire entirely, without using tools.

Thread at least five zip ties between the rim and the tube/tire, all the way through the channel, equally spaced around the rim.

For each zip tie, press the two tire beads together, with the tube inside the tire. Snug the zip tie so the beads are held closed together. This will allow the beads to drop into the channel at the center of the wheel.

It is now possible to pull the tire off-center and work it over the rim. A flat-blade screwdriver can be used, but hand strength may be sufficient.

The zip ties can be salvaged by inserting a knife blade between the tongue and tail to disengage the ratchet of the zip-tie fastener.