He committed major shirk and met all conditions of repentance but still feels like it isn’t enough

When he was around 14 years old, he prostrated to other than allah as a joke with his friends not knowing this was major shirk, since then he has read the Shahada multiple times and prayed salat ul tawbah multiple times and repented but he still feels like he has left the pale of Islam and gets a lot of waswas saying that there is no repentance for him and that no matter what he does Allah will not forgive him, even though the Quran states otherwise. What is the ruling on this? Is he still a Muslim? Also, is performing ghusl fard, as he’s heard people say that performing ghusl after committing major shirk is mandatory. And lastly, are his good deeds void now? He has been praying taraweeh and staying up reading Quran and praying at night since the last ten nights of Ramadan started, are his deeds still valid?