Look here first, if you can not find answer to your question, go to support in Discord
No, you should not. If you see gas exception, that means that your transaction will be reverted. Do not try to submit transaction anyway because you will only lose your eth as due to gas exception.
If you can not vote with your LP tokens, then check the proposal creation date. If you minted your LP tokens after the proposal was created, then you're not able to vote for security reasons. Check Vote on Proposal
Anyone can execute proposals after they finished and Quorum and Min Approval were met. So anyone is able to push on "Execute" button and changes will be implemented. Check Execute proposal
Check if you're eligible to invest and your wallet in the list of wallets available for investment.
Check if you've reached max deposit value per wallet. Restrictions (Min and Max deposit size) are applied to sum of all deposits from your wallet.