Thank you for your enquiry.
I am unaware there are any rules on how long he can stay in the UK before travelling abroad on holiday. But when applying for settlement after 5 years he will need to meet residential requirement.
I can only answer further questions when you have rated.
He should only be out of the country for short visits. The residency requirement is the number of days you are expected not to have been out of the UK if for example in the future your husband wants to apply for British citizenship. In spousal cases it is no more than 270 days in the last 3 years.
Short visits is acceptable
Depending on how often he makes these visits. But in general 4 weeks holidays are acceptable.
This is a decision you would have to make based on the information I have already given. If you are concerned you should seek independent legal advice.