Bam Margera Desperate For Relationship With Son Amid Drama With Estranged Wife

Bam Margera is desperate to develop a relationship with his son, Phoenix ... but the former "Jackass" star says his estranged wife isn't having it.

Bam's attorney, Peter W. Thompson, tells TMZ ... Nikki is not allowing Bam to talk to his son through FaceTime or phone calls, and she's completely cut off all contact.

We're told the last communication between Bam and Phoenix was over 2 months ago, on March 29, when Bam came to California to visit his son.

Of course, that was the day we got video of Bam screaming at Nikki in a Burbank restaurant where she was having lunch with Phoenix.

Since then, we're told Bam hasn't seen Phoenix or been able to speak with him.

And, get this ... we're told Bam has Christmas gifts for Phoenix that he's been unable to give him. Despite Bam's attempts to get the gifts to his son -- 5 months after the holiday -- we're told Nikki won't accept them, even rebuffing Bam's offer to have other people drop off Phoenix's gifts.

As we first reported ... Nikki filed for legal separation back in February, citing irreconcilable differences and asking for legal and physical custody over Phoenix, as well as spousal support.

Bam's attorney says at one point they were trying to set up a schedule where Bam and Phoenix would FaceTime every other day, but it never materialized.

The way Bam's camp sees things ... it's safe for him to interact with Phoenix on FaceTime or on the phone, and it's "completely unreasonable" for Nikki to not answer the calls.

Bam's voiced his complaints with a judge but was shut down ... and Nikki shaded him in her legal response, claiming he can see their son as long as he's in California and not under the influence.

Meanwhile, we're told Bam's still supporting Nikki financially ... paying for the car she's driving and footing the bill for her home.

Bottom line for Bam ... he's willing to work with Nikki and her attorney because he wants to see his kid, even if it's just virtually.