For the actual questions, yes the overvoltage could cause damage, and yes you should use resistors. The problem is, TTL outputs are not meant to be connected to analog VGA inputs, not even with resistors.
CGA uses TTL outputs for RGBI and HV signals. The signals are buffered by a 74LS244 line driver.
VGA input uses 75 ohm termination for the analog RGB lines, and HV sync inputs are TTL compatible digital inputs. The RGB voltage 100% level is 0.7V into the 75 ohms, or 9.3mA.
So the sync signals are electrically compatible, no reason to change that. They can be directly connected.
The problem is that a TTL output cannot be expected to drive out 9.3mA into any load. A modern LS244 buffer, which by the way has much stronger output drive ability than standard LS TTL chips that are not buffers, is specified to drive out only 3mA, and the only guarantee you get is that the voltage is at least 2.4V, or 3.4V typically.
So while the theory is that CGA outputs 5V logic signals and can be divided down to 0.7V through a 461 ohm resistor sounds good, there is no reason to assume it will work or even survive without damage.
The CGA TTL output is not intended to drive 536 ohm load. It can't drive the required 9.3mA to VGA analog input, at least not without serious overload and unpredictable output voltage, so at least the series resistor should be much lower than 461 ohms in practice.
Another problem is that a VGA monitor will likely expect VGA resolutions only and may not lock on to any signal it does not recognize from the list of supported formats. However if this is a TV with a SCART input, it might share the analog input so it could understand TV resolutions from VGA input as well, but do not expect it to work.
VGA is a video signal with about 31 kHz horizontal rate, 70 or 60 Hz refresh rate depending on resolution. CGA is a 15 kHz video signal more closely related to 60 Hz 525-line interlaced TV scanning system, but it is not interlaced but progressive scan.
Many digital TVs don't actually expect such a low format and even if it works with standard TV formats it may not handle the 200-line progessive 60 Hz. Since the TV has a SCART input, it indicates support for 50 Hz TV formats so it may have poor or no support for 60 Hz TV formats.
Same for EGA. Uses same LS244 logic buffer. EGA video has 22 kHz horizontal frequency. Unlikely that TVs or monitors would lock on to the signal as it's practically never used on VGA connector.