With frame and portable pumps, theres are rare breed of high quality ones that can pump up to high pressures with EASE, whereas the rest for some reason (beyond the laws of physics) just don't work.
You have to just read the forum, and find a pump which is recommended by someone, and you know that model will be good to use.
With the valve stem problem, frame pumps usually come with a hose so it doesn't put pressure on the valve stem. In a new pump you could look for a hose.