Am I entitled to break off the engagement due to the suitor's change in behavior and my desire not to complete the marriage?

It is advisable to be patient with a suitor who possesses religiosity and good character until he is able to afford the expenses of marriage. It is permissible for a husband to allow his wife to work in a permissible field, whether by stipulating a portion of her salary or without such a condition. However, if the wait becomes difficult or if she no longer desires the suitor, there is no sin in breaking off the engagement. The preponderant opinion is that one who seeks guidance (through Istikhara) should proceed with the matter after Istikhara, unless Allah diverts him from it.