I wouldn’t worry about the suggestion that this is blackmail. Blackmail is unwarranted demand with menaces. Your demand is not unwarranted.
If he hasn’t protected the deposit, you are entitled to 3 times the deposit as compensation for the failure to protect plus the return of the deposit.
He cannot give you valid notice until the deposit has been protected but even if it has been protected late, you still have a compensation claim.
There are loads of solicitors crying out for this work because it’s so easy to bring and very difficult to defend.
If you Google
Tenant deposit protection solicitor claim
You will find loads looking for the work.
Find one that would also deal with the landlord’s disrepair claim at the same time because you are entitled to substantial compensation in respect of the damp et cetera. Further, once you have intimated the landlord’s disrepair claim, he cannot then give you notice because that is classed as revenge notice that is invalid until such time as the disrepair has been resolved.
Thank you for letting me assist you with your legal question. I am glad that I was able to help.
I am not certain whether that answers the question for you or not, but I am happy to answer any specific points arising from this.
It will be my pleasure to help you again either further with this or any future questions you have