first - nice work .. that is a real good start to pentatonic based improv
do you have a backing track chord progression in Bb to work over? .. if not, record one and put it on infinite loop repeat ... the most MOST important thing about improvising is making the notes SAY something in the context of a chord progression ... if you are just noodling without context, you better be as good as eddie van halen (a la eruption) if you wnat to make some kind of musical statement ...
you need to leave out those low note double stops and heavy chord like things .. they really do not have a place in the idiom you are dipping your toe into at this time .. in the future, when you are a master of the domain, you wil be able to put whatever you want in and it will sound good .. but for now, you need to stick to the shallow end
do you only downpick? ... there is something about the attack of your notes that doesnt breath or bounce ... you really want to do some solid picking exercises up and down .... do not go for speed ... go for excellent finger tone and precision ... play scales with alternate pick strokes both straight and swung eigth notes ... i also think you need to play a bit slower until your right hand/left hand synchronization gets better .. you still hit a lot of flub notes cause you pick before your left hand is really in the proper position
i do not think your high notes sound 'chinese' on the recording ... if they sound that way live, roll the highs back on the tone control or amp EQ settings, use heavier gauge strings,
as for note choice, yeah, you want to learn to play in more than one position of the pentatonic 'box' .. learn two or three or more positions .. then practice lines that connect them flowing up and down the neck between them at 'pivot' points ...
when you play against the chord progression, play long slow whole notes of every note (a coupla octaves) in the scale againt the chords .. get the sound of the notes in your ear .. then do the same with intervals of the scale ... think of the notes as words .... think of the intervals as phrases ... think of strung together intervals as sentences .. you have to get these building blocks in place before you can 'say' anything with your improvs
and dont be afraid to put some jazzy notes in and around the straight pentatonic scales .. this will spice up the jazziness of your improvs
keep pushing on .. you are on the right track