About Shreemad Bhaagavatham
Śrī Caitanya Mahāprabhu declared, śrīmad-bhāgavataṁ purāṇam amalam: “Śrīmad-Bhāgavatam is a spotless Purāṇa.”
About Multiple Deities
Śrīmad-Bhāgavatam 4.7.54:
trayāṇām eka-bhāvānāṁ
yo na paśyati vai bhidām
sarva-bhūtātmanāṁ brahman
sa śāntim adhigacchati“The Lord said: One who does not consider Brahmā, Viṣṇu, Śiva or the living entities in general to be separate from the Supreme, and who knows Brahman, actually realizes peace; others do not.”
Śrīmad-Bhāgavatam 12.10.22:
yaḥ kaścaneśo balino ’ntakoragāt
pracaṇḍa-vegād abhidhāvato bhṛśam
bhītaṁ prapannaṁ paripāti yad-bhayān
mṛtyuḥ pradhāvaty araṇaṁ tam īmahi“These devotees do not differentiate between me, Lord Viṣṇu, and Lord Brahmā, nor do they differentiate between themselves and other people. Therefore, we praise you.”
About Brahma being Born from the Navel of Vishnu
Refer to Spider-Web analogy of creation.