Is this even worth hiring an attorney?

Yes. You can get jail time for violating probation. Hire an attorney to help you avoid that.

Would warrant be invalid and create jurisdictional issues

Cases don't usually get dismissed for something like a missing signature since they could just sign the document at a later time. Hire an attorney...

No but a prosecutor could try using as evidence that you did possess a firearm. Rather than have to defend against felony chargea, get this...

My son was arraigned yesterday and was given a bond, but he has a active hold on him.

See if the county jail will tell you what the hold is. It wI'll probably be easier for you to hire an attorney who will be able to sort through...

When you were sentenced to probation, you should have been given an "Order of Probation." Check it to make sure it doesn't prohibit the possession...

Possession of marijuana with a legal hand gun

It depends on a number of factors that aren't clear at this point. Hire an attorney immediately to begin gathering evidene and prepare your defense.

On felony probation and than break into safe twice at a store what are the possible charges for this?Is it robbery,safecrack?

Hire an attorney immediately. Safecracking is a serious crime and his guidelines will be high because it was committed while on felony probation.

My son was charged with possesion of heroin, He does not do heroin, it was found on the floor in the back seat, what can i do...

It sounds like an unconstitutional from the limited facts you've shared. Even if a judge admits the evidence, it doesn't sound like the prosecutor...

Will I get charged for Trespassing even though i was not arrested?

Possible but unlikely since the police weren't called at the time.

You don't have an expectation of privacy in public. The police don't need a warrant to simply follow you around.