Check out this post which completely solves this issue (using JSON messages)
Arduino mega to esp8266 communication via TX RX
But you can send lines of plain text just as easily.
The 64 char problem is the RX buffer overflow on the Wemos side
The solution in the post referenced above is to allocate a bigger SoftwareSerial buffer
I used 256 bytes but see no reason you cannot increase that.
The SerialComs software is tolerant of long delay() on either side. It will just reconnect.
It also works well with SoftwareSerial as it does not allow send/receive to happen at the same time.