Britney Spears’ boyfriend is a “deadbeat dad” who allegedly “neglects” and “denies his children” — at least, according to his ex and the mother of at least 5 of his kids,RadarOnline.com has learned. As this outlet reported, Spears and Paul Soliz Jr.got into an altercation last week at Chateau Marmont, with police and paramedics showing up at the scene. Paul’s criminal post — which includes being charged with felony possession of a firearm in December 2022 — came to light after the situation, and, now, his ex, Nicole Mancilla, 36, is speaking out about his character. Mancilla claimed Paul cheat…