1 year old with stained top teeth?!?

Background my son is nearly 1 year old with 8 teeth. We started wiping his mouth with a wet washcloth prior to him having teeth then after he had a few we started using infant/fluoride free toothpaste and a toothbrush each night at bath time...

He was born with a complete tongue tie that prevented him from being able to feed and it was revised as a newborn... but we suspect he may also have a lip tie but doctors have always disregarded it.

He never lets us lift his upper lip and does not naturally show his top teeth when he talks or smiles. We started noticing them yellowing and switched to using filtered tap water rather than distilled water, using a kids toothpaste with fluoride (size of a grain of rice) and brushing right before bed even though he throws a fit!

We’re in the process of weaning to cows milk and off bottles and onto sippy cups...

We never offer sweets other than fruits and he never drinks juice. Only water or milk/formula...

I feel like I’m doing all I can but his teeth are just so bad and he’s loses it when we brush his teeth so we can only do so much...

Please help 😭

His dental insurance doesn’t activate until after his 1st birthday so his first appointment isn’t scheduled until the beginning of July.

HELP!