Without console and/or the reset button, you're out of luck. All recovery routes require some form of this. Even to get the device to boot from USB to recover requires a press of the reset button at turn on.
I'd try the USB boot with turning the device on and pressign the reset button just in case the reset block is set and takes effect after boot.
the re-installation at the loader prompt would be the right procedure. For me it seems that your installation image is corrupted. Please download a new image and perform a checksum check, if it matches with the provided checksum on the Juniper download site.
E.g. for JUNOS 18.2R3, the command you should use looks like:
I can assure you that the "loader> install file:///" command is the right one. Please check some other USB devices, make sure they are error free and that they are FAT32 formatted. After copying the JUNOS image to the USB device, please verify the checksum again, to make sure that there were no errors during copying.
I did succeed with a Sandisk USB and fimware "junos-srxsme-19.4R1.10.tgz", it even let mesee the configuration even though i didnt think that it was possible because the customer it very tightly locked down, but it worked 🙂