Must the first salary be given as charity after the current work conditions have improved and I feel comfortable in them, or should I wait for another job in which the original vow will be fulfilled, knowing that the financial situation is not good?

It appears that what is meant by an improved salary and a sense of security is what you tied your vow to. If that occurs, you are obligated to fulfill it. However, if changing workplaces is important to you for some reason, then nothing is binding upon you, because intention is considered a restriction and specification in vows, just as it is in oaths.