I've already been through all of the points you've raised, probably with you.
The seal is given when someone, as a result of salvation, truly believes. Believing doesn't bring salvation; it comes from salvation.
Being indwelled by the Holy Spirit is different than being sealed and occurs when someone is born-again through salvation.
DT 20:19 was a choice given under the Old Covenant of works, which choice, is one of the covenant's required works.
In the New Covenant, however, no such choice on the part of the recipient was permitted. God made all of the choices - it was/is a unilateral covenant. The "all" of 1 T, 2:3-4, represents "all" the Father gives to Jesus for salvation. If the Father desired everyone to become saved, He would then give everyone to the Son, but He doesn't. It is on the basis of having been given to the Son, that specific individuals become saved. Those who are given, cannot, not, become saved; those not given cannot become saved. MT 23:37 is speaking about God no longer using the corporate Jewish church to manifest His true salvation message due to their spiritual fornication and the worship of other Gods in failing to recognize Jesus as Savior. That is why MT 23:38 says "your house is left unto you desolate". Their "house" was left desolate because God moved the teaching of the salvation message away from their house - the Jewish corporate church- making it desolate that no one would/could be saved through it - and placed it into the hands of the disciples. The "calloused" heart ETC, represents the unsaved heart. When, and if, someone becomes saved, through the New Covenant, a new heart given them by God. The same with the eyes. Notice that Mat 13:15 says "but blessed are your...' that means their eyes first had been blessed, in order for them to be able to spiritually see, spiritually hear, etc. Only from that blessing, were they able to do so.
Believing is fallible, so we need to believe whatever harmonizes with whole of GW, beginning with God's all-lovingness, but you do not even affirm that truth! Instead, you say that 1TM 2:3-4 teaches God loves only those the Father gives to Jesus in direct contradiction to it saying that God loves and wants to save ALL people!!! You rant about God hating most of humanity, because God's love even for His enemies must not be in your heart. Sad, making being indwelled and sealed by the HS problematic. Beware the one who can appear as an angel of light.