This is my translation from the last words of the 3rd line to about a third of the 5th line.
mentioned                  -  mentioned
dicti                      -  to say, speak, utter, tell, mention, relate, affirm, declare, state, assert
quous                      -  if any, It could also be short for the word 'quousque',:- until what time, till when, how long; or (quo usque) [how long? how far?].
Lancelot Armstrong         -  Lancelot Armstrong
durank?
sua                        -  his, their, their own, his own, it's.
bita?                      - 
possess                    -  possess
fuerunt                    -  were, have been, they were, there were, been.
per                        -  before, aforesaid,
prefatum                   -  the said 
Francis Armstrong          -  Francis Armstrong
erus? looks like opus?     -  Master of a House, Proprietor, Master of a Family, Owner, Lord (Laird?), Sweetheart, God. 
nepotem                    -  grandson, the grandson of, nephew, the nephew of
semper                     -  always, eternally, ever, perpetually, fore ever,
ab                         -  from the, by the.
erus? looks like opus?     -  Master of a House, Proprietor, Master of a Family, Owner, Lord (Laird?), Sweetheart, God.
decessu                    -  departure, decease of, decease,
tanquam                    -  as much as, so as, just as, like as, as if, so to speak
hereditary properties      -  hereditary properties
earundem?                  -  the same, same, their, of their.
possess                    -  possess
sunt?                      -  to be, exist, live
sicuti                     -  as, as he, as it, just as.
etiam                      -  also, is also, also the.
pre                        -  aforesaid

??
dicti                      -  to say, speak, utter, tell, mention, relate, affirm, declare, state, assert
quous                      -  if any, It could also be short for the word 'quousque', :- until what time, till when, how long; or (quo usque) [how long? how far?].
Lancloti                   -  Lancelot
hereditary property        -  hereditary property
et                         -  and, and his,
possessors                 -  possessors
dictarum                   -  of the said, said, aforesaid, the aforesaid.
terrarum                   -  of the lands.