Yes it is safe. As far as I know, when you give someone your address they can not look at the blockchain and see how much monero you have or the addresses you sent it to.
However for more privacy it is recommended to create a subaddress for each party you plan to interact with. For example you can have one subaddress for each different exhange you deal with ...
The Monero is on the blockchain.
To recover the Monero seed see the section "Seed recovery" in this Ledger guide:
Not easy but remember, the Monero are on the blockchain so there is time to recover the seed. They are only lost if your Monero seed is lost.
Please advise if it's safe to share my Monero Wallet Address with them.
Yes. It is safe to share a wallet address with someone who wants to send you money. If you don't give them a wallet address they cannot send you money.
...can they withdraw funds from my account with my address?
No. They would need your private keys (or your seed to restore) to spend ...
If you are fully synchronized but your block height is not the same as other people, you are not fully synchronized or are connected to bad peers. Check against know block explorers (e.g. xmrchain.net) or remote node operators (like xmr.to).
As repeatedly pointed out, churning in most cases is actually harmful to your privacy. The only exception I'm aware ...