Can I be arrested for non-payment of alimony after losing my job?

As the person seeking a modification of alimony, the burden and responsibility of moving your case forward is on you, not the court. Assuming you properly prepared and filed your modification petition, you still have to serve it on your former spouse, generally by the sheriff or a private process server, and then they have 20 days to file an answer to your petition. If they don't file a response within the time allowed, then you have to seek the entry of a default against them. Either way, you would still have to engage in financial disclosure, just like in your divorce case, and file a financial affidavit, exchange certain financial documents (like tax returns, bank and credit card statements, etc.). In most circuits in FL, you would also be required to attend mediation in advance of trial, and in some circuits, before you are permitted to ask the court to schedule a trial date. Consult with an attorney to discuss the specifics of your situation and your options. It would be well worth paying for a half hour or so of an attorney's time to get some assistance.

If you filed for modification then set the matter for hearing the court will not set your hearing for you. Use of a lawyer is recommended.

Yes, you can be held in contempt of court for not paying your support obligation, and jailed for up to 180 days. Get an attorney on your side.

Yes there is an emergency hearing that you can request. Rather than just not pay your alimony I would absolutely agree with you that you should go to court on an emergency hearing to let the judge know what is going on. Good luck.