Questions about rhythm and phrases

For the rhythm question would be try to practice with a metronome and put an accent on 2 and 4 because that’s usually where the snare is. When you play along to a song try to listen to the snare because that’s kind of your pivot as to where you are, as I said when you count the snare usually is in the 2 and 4 beat. Like one TWO three FOUR, where capitals imply a snare hit. This doesn’t count for all songs but it’s a good basic to start with.
A good way to know how long your phrases should last is by trying to use rests in your playing. If you listen to most blues greats you will notes there is a lot of quiet time where they don’t play anything but let it rest for a bit. As far as your phrases always being the same speed. That’s not actually Nescecarily bad. Just make sure you pay attention to other forms of Dynamics(like loud/soft and stuff like that). My basics as far as Dynamics in a solo usually is go slow at the beginning and kinda go gradually start throwing in speedier licks and go the fastest during the ‘climax’ of your solo.
I think the easiest way for me to practice this and knowing when to stop would be to listen to yourself while you play(this also takes some time to be able to do) and just stop the phrase when you get close to boring yourself when you listen to your own playing. This helped me a lot when I’m improvising.