To summarize, here my experience after burning pro-minis for an equivalent value of 35 dollars:
1. USB cable + FTDI breakout + "Upload command"
Works solid as a rock. Doesn't matter if the TFT is attached or not. Drawback: the original bootloader from Sparkfun is a dinosaur, it occupies 2K of the 32K of flash memory available.
2. USBasp dongle + "Upload Using Programmer"
Works with the TFT attached (but you have to use a 10K resistor on the MISO line). Drawbacks: sometimes the sketch won't start during a series of power-cycles.
3. USBasp dongle + "Burn Bootloader" + "Upload Using Programmer"
Two sub-cases:
3.1 It will destroy your pro mini if the TFT is attached.
3.2 It will works if the TFT is completely disconnected. Drawback: the sketch won't start when the TFT is connected.
Note: in both cases 2 and 3 I was trying to use almost all of the flash memory available (32768 bytes), so I was using the option "Bootloader=No"
EDIT
About point 3.1, I've discovered a wire not firmly inserted into the breadboard. Maybe that was the problem. I have to redo the test for final confirmation