I'm not sure its wise to piss off the guys who have a vote to impeach you and/or remove you from office.
Sounds like he is trying to rein his party but loyalty will only go so far. Silence from all but the most rabid Trump supporters in Congress should really worry him. None want to go on record to defend him as the testimony summaries come out.
Trump might want to put House members on the record with an impeachment vote, but unless he resigns, he will force the GOP Senators to vote as well and depending on public opinion that may not be good for their re-election campaigns if the House can put together a solid and convincing case. I suspect at some point they will get tired of defending him and have to decide how flexible their principles really are.