You do indeed need to keep your own lawyer! I don’t know much about law admittedly, but you do need someone who has your best interests at heart and I doubt a lawyer serving both of you can be the advocate you need (especially one your husband hired... based on what, exactly? Consider the source, here).
You’re right that there’s no need to delay the divorce - your husband is just being inconvenienced (and shocked, shocked I tell ya!) by the consequences you’re setting in motion for what he did. The sooner it’s over, the sooner you can start healing.
And don’t hate yourself for being “nice”. My T says I’m a pushover, too - I also hate it, so I do sympathise with you, but we would be well served to look at it as an opportunity to learn to have stronger boundaries.
This situation is tough, but it sounds like you’re determined to get through and that’s a great start.